Transparent layer facilitates making interference photograph, located between reflector and photosensitive layer

ABSTRACT

The invention discloses that a photograph with a 3-dimensional image results when the non-angular reflector (of mercury) used in the Lippmann process of color photography is replaced by an angular reflector; the preferred form of the angular reflector is a retro-reflector. 
     A photographic system is described which produces photographs with 3-dimensional images. The photo-sensitive element records the interference patterns of light waves, and the system is an improvement over the Lippmann process of color photography which produces photographs with 2-dimensional images. A photographic system is also described that produces a photograph with a 3-dimensional image from 2-dimensional cross sections of a subject; the system is useful in medical imaging. During exposure, motion of more than one wavelength of light is permissible between the subject and lens or the lens and the photo-sensitive element. 
     These improvements result from the use of a particular type of angular reflector which is a retro-reflecting sheet. This sheet is used in place of the non-angular reflector (of liquid mercury) used in the Lippmann process. The retro-reflecting sheet is covered with small sub-reflectors that are in the form of cube corners; there are 47,000 cube corners per square inch. 
     Improved angular reflectors are described. A diffraction grating is one of them. A way of reducing the speckle produced by a laser illuminated subject is described by the use of a moving diffuser. A transparent thermoplastic, water soluble glue is described that has a refractive index of about 1.5 and it softens at less than 200 degrees F.

CONTINUING DATA AS CLAIMED BY APPLICANT

This application is a CON of Ser. No. 08/292,318 Aug. 19, 1994, now U.S.Pat. No. 5,449,597, which is a CON of Ser. No. 08/168,274 Dec. 15, 1993ABN, which is a CON of Ser. No. 07/737,889 Jul. 25, 1991 ABN, which is aCON of Ser. No. 07/291,535 Dec. 27, 1988 ABN, which is a DIV of Ser. No.06/920,782 Oct. 20, 1986 U.S. Pat. 4,835,090 which is a CIP of Ser. No.06/699,504 Feb. 8, 1985 ABN which is a CON of Ser. No. 06/539,640 Oct.5, 1983 ABN which is a CON of Ser. No. 06/348,610 Feb. 12, 1982 ABNwhich is a CON of Ser. N. 06/072,209 Sep. 4, 1979 ABN which is a CON ofSer. No. 05/072,197 Sep. 14, 1970 U.S. Pat. No. 4,178,181 which is a CONof Ser. No. 04/544,275 Apr. 21, 1966 ABN.

RELATED PUBLICATIONS

(James, 1948.) James, T. H., and Higgins, George C., Fundamentals ofPhotographic Theory, Wiley, New York, 1948, page 15.

(Lipton, 1965.) Lipton, L., Popular Photography, March 1965, pages63,98,99.

(Mark, 1939.) Mack, J. E. , and Martin, M. J., The Photographic Process,McGraw Hill, New York, 1939, pages 168,180,181, 364.

(Mees, 1937.) Mees, C. E. K., Photography, Macmillan, New York, 1937,pages 63, 64, 65.

(Mees, 1942.) Mees, C. E. K., Theory of the Photographic Process, 1sted., Macmillan, New York, 1942, pages 34, 35, FIG. 14.

(Mees, 1954.) Mees, C. E. K., Theory of the Photographic Process, 2nded., Macmillan, New York, 1954, pages 23, 27, 28, 29, 34, 35.

(Mees, 1961) Mees, C. E. K., From Dry Plates to Ektachrome Film,Ziff-Davis, New York, 1961, page viii.

(Mees, 1966.) Mees, C. E. K., Theory of the Photographic Process, 3rded., Macmillan, New York. 1966, pages 31, 36, 37, and cover.

(Sears, 1946.) Sears, F. W., Principles of Optics III, Addison-Wesley,Cambridge, Mass., 1946, pages 159, 160, 161.

(Wall, 1922.) Wall E. J., Practical Color Photography AmericanPhotographic Society, Boston, 1922, page 224.

(Wood, 1962.) Wood, R. W., Physical Optics, Macmillan, New York, 1962,pages 214, 215.

The foregoing references are explicitly made a part of thisspecification as background information for the Lippmann process.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is in the field of photography, and moreparticularly relates to layered photo-sensitive elements, where one ofthe layers is a photo-sensitive layer and where one of the layers is areflector, to methods of preparing these elements, to methods for theuse of the elements, and to methods of using the resulting photographs.

2. The Prior Art

The conventional Lippmann process of color photography was invented byGabriel Lippmann in 1891. The process was different in many ways fromordinary photographic processes. Without dyes, color photographs wereproduced based on the principles that produce color in soap bubbles. Anextraordinarily fine grained, black-and-white film was used. While inordinary photography one seeks to suppress the reflections off the backside of the photo-sensitive element (film or plate) during exposure bythe use of a dark anti-halation coating, the Lippmann process requires amirror rotor of liquid mercury to back the film. Lippmann's processproduces a photograph with a 2-dimensional image.

Some Details of the Lippmann Process with Comments

The Lippmann Light-Sensitive Element:

1. The Lippmann light-sensitive element is a layered assembly thatincludes (a) a light-sensitive (emulsion) layer, (b) a light-sensitive(emulsion) layer support, and (c) a parallel reflecting layer of liquidmercury. These essential items are in FIG. 1 that shows the Lippmannlight-sensitive element 101, mercury reject layer 102, light-sensitive(emulsion) layer 103, emulsion layer support layer 104, camera housing105 with lens 106, subject 107, light source 108, and light from thesubject 109.

2. The mercury reflector is a non-angular reflector in that it reflectslight in the same direction as the specularly reflected ray from thenominal surface, not at an angle to the specularly reflected ray fromthe nominal surface. (An angular reflector reflects light at an angle tothe specularly reflected ray from the nominal surface.) The mercury is aspecular reflector. (The surface of the mercury is indeed the nominalsurface. Angular and non-angular reflectors are discussed elsewhere inthis disclosure.)

3. The light-sensitive (emulsion) layer contains light-sensitive grains.

4. They are characterized as being spherical in shape.

5. They are suspended within a transparent material (gelatin).

6. Their average diameter is equal to or less than a "given value."

7. Their average diameter is about 1/8th of the shortest wavelength orlight to be recorded, or less.

8. Their average diameter is about 50 nanometers or less, whenphotographing in the visible light range (400 to 700 nanometers).

9. They contain at least one silver halide. Example: silver bromide.

10. The minimum thickness of the light-sensitive (emulsion) layer mustbe at least as thick as 2 planes (described later) for the process towork. The longer the wavelength, the farther apart are the planes. Theminimum thickness of the light-sensitive (emulsion) layer is at leastequal to the longest wavelength of light (in air) to be recorded dividedby 3 (in order to be at least as thick as 2 planes).

The Method of Using the Lippmann Light-Sensitive Element Includes theFollowing Essential Steps During Exposure:

11. The light-sensitive element is exposed to light from only one sideof the element. FIG. 1 shows the light-sensitive element 101 beingexposed to light from only one side of the element.

12. The incident light from the subject and its reflection interfere,within the light-sensitive (emulsion) layer, causing an interferencepattern of light waves to exist within the light-sensitive layer duringexposure.

13. These patterns are a series of parallel planes or light (separatedby planes of darkness) and are parallel to the reflecting surface andlayers of the assembly. The parallel planes of light are spaced at about1/3rd of the waveleth (in air) of the light. The light-sensitive layermust be able to record these planes that are spaced at about 1/3rd ofthe shortest wavelength (in air) of the light to be recorded.

14. Thus, during exposure, interference patterns (planes) produced bylight waves are present within the light-sensitive layer. They areparallel to the reflecting surface (that is the nominal surface),regardless of the angle the incident ray makes with the reflectingsurface.

15. The light-sensitive grains are required to be able to record theseinterference patterns (planes).

16. The light-sensitive grains do record these interference patterns(planes), which are parallel to the reflecting surface. Or, therecording of the interference patterns of light waves within thelight-sensitive layer takes place by exposing the light-sensitivegrains.

The Method of Using the Lippmann Light-Sensitive Element Includes theFollowing Essential Steps After Exposure:

17. The reflecting layer is removed.

18. Viewing the photograph (or detecting the image) requires theinterference of light waves.

19. The image is stored within the emulsion layer as partiallyreflecting layers (at least 2) that are parallel to the emulsion surfacerather than as relief on the surface of the emulsion.

Viewing Problems of Photographs

As background information the reflections from various types ofphotographs is considered.

Mat Finish Photograph Viewing Problem.

The reflections from a photograph with a mat finish are shown in FIG. 2;it shows the photograph 201, a small portion of the photograph 202, alight source 203, an incident light ray 204, diffuse reflections fromthe surface 205 which spread out equally in all directions, and diffusereflections 206 from the image beneath the surface which spread out inall directions. From any viewpoint 207, some surface reflections 205 areseen along with the image reflections 206. The mat finish photograph hasthe advantage of eliminating very bright surface reflections, but thecontrast between the lightest and darkest parts of the image is not asgreat as in a photograph with a glossy finish.

Glossy Finish Photograph Viewing Problem.

The reflections from a photograph with a glossy finish are shown in FIG.3; it shows the photograph 301, a small portion of the photograph 302, alight source 303, an incident light ray 304, the specular reflectionfrom the surface 305 (There is only one reflection from the surface andit is in the direction of specular reflection. Specular reflection isthe kind or a reflection that occurs from a common household mirror orfrom a polished metal surface, as from silver or chromium), and diffusereflections 306 and 308 from the image beneath the surface. From anyviewpoint 307, no surface reflections are seen, unless that viewpointhappens to be from the direction of specular reflection 309 where theviewer will see a large surface reflection 305 and a small imagereflection 308; in this case, the specular surface reflection 305obscures the reflection from the image, 308. At all viewpoints, otherthan at 309, the viewer see only the reflection 306 from the image belowthe surface, and the contrast between the lightest and darkest parts ofthe image is great. The problem of the surface reflection obscuring theimage reflection is easily solved by tilting the photograph or bychanging the viewing position so that the specular surface reflection305 is out of the way. One automatically does this when viewing a glossyphotograph.

Lippmann Photograph Viewing Problem.

The reflections from a standard Lippmann photograph are shown in FIG. 4:it shows the photograph 401, a small portion of the photograph 402, alight source 403, an incident light ray 404, the specular reflectionfrom the surface 405, and the specular reflection from the image beneaththe surface 408. (Because the image is a series of partially reflectingplanes parallel to the surface of the photograph, the specularreflections from the surface 405 and from the image 408 are in the samedirection.) From any viewpoint 407, no surface reflections are seen,unless that viewpoint happens to be from the direction of specularreflection 409 where the viewer will see the surface reflection 405 andthe image reflection 408; the specular surface reflection 405 obscuresthe reflection from the image, 408. At all viewpoints, other than at409, the viewer sees neither the reflection 408 from the image below thesurface nor the surface reflection 405. The problem is that the surfacereflection 405 obscures the view of the image reflection 408 frombeneath the surface. It is not easily solvable by tilting the photographor by changing the viewing position so that the reflection from thesurface 405 is out of the way and the reflection from the image beneaththe surface 408 is seen; the image is invisible from viewpoints 407. Asshown in FIG. 4, it is not possible to view the Lippmann photographimage 402 without the surface reflection 405 obscuring the the view ofthe photographic image.

The problem is especially acute when the Lippmann image 408 is weak andthe surface reflection 405 remains strong.

It is one of the major problems of the Lippmann process.

U.S. Pat. No. 4,178,181 column 6, lines 34 through 38 states: "One ofthe disadvantages of the standard Lippmann photograph is that theviewing angle is critical with respect to the light source. Lippmannreported that the colors are visible only in the direction of thespecular reflection, and are invisible in every other direction."

The Problem.

What one wants to do is to be able to see the image reflection 408without seeing the surface reflection 405 at the same time. In otherwords, one wants to view the photograph's image 402 without the viewbeing obscured by the surface reflection 405. (If one could view theimage reflection 408 without seeing the surface reflection 405, theresult would be profound in that all the light reflected from the image408 is in one direction, and therefore extraordinarily bright, and thecontrast between the lightest (extraordinarily bright) and darkest parts(virtually no light) of the photograph would be greater than in eitherthe mat finish photograph or the glossy finish photograph cases of FIGS.2 or 3.)

Prior Art Solution (Wedge).

Prior art attaches a wedge to the completed Lippmann photograph of FIG.4 result in the configuration of FIG. 5 which shows the Lippmannphotograph 401, a small portion of the photograph 402, a light source403, an incident light ray 404, the wedge 501, the specular reflectionfrom the surface of the assembly 505, the specular reflection from theimage 508, and the viewing position 509 from which the image reflection508 can be seen. All other viewing positions, as shown by 507, seeneither the image reflection 508 nor the specular surface reflection505. The image is extraordinarily bright, and the contrast is great.Wedges have been made of glass and of liquid.

Prior Art Solution Is Impractical.

The use of the wedge is the only prior art (prior to 1966) solution tothe surface reflection problem known to the inventor. A 10 degree glasswedge that covers an area of 4 by 5 inches is over 1/2 inch thick, atits thickest point, weighs over 1/2 pounds and is, of course,inflexible. For these reasons, the inventor believes the wedge is animpractical solution because the photograph cannot, from practicalconsiderations, be placed in conventional photograph album. The use ofthe wedge is also illustrated in U.S. Pat. No. 4,178,181, FIG. 3a.

SUMMARY OF THE CLAIMED INVENTION

The invention is a method of making colored photographs with3-dimensional images (or 3-dimensional photographs). It is basically animprovement over the Lippmann method of colored photography whichrecords the interference patterns of light waves in a photo-sensitivemedium.

The Lippmann method makes photographs with 2-dimensional images (or2-dimensional photographs). The interference patterns of light wavesthat are recorded are stacks of parallel planes that are parallel to thenominal surface of the reflector that he used during exposure. Thereflector that he used was a plane, specular reflector of liquidmercury.

The invention method makes photographs with 3-dimensional images. Theinterference patterns of light waves that are recorded are stacks ofparallel planes, as in the Lippmann process, but are positionedperpendicular to the incident light rays, and are generally not parallelto the nominal surface of the retro-reflector.

The principal modification of the Lippmann process is the substitutionof a retro-reflecting layer for the specularly reflecting layer ofmercury. The peculiarity of the retro-reflector is that it reflects anincident light ray back along the incident light path rather than in thedirection of specular reflection. It is thus an angular reflectorbecause the light reflected from the reflector is at an angle to thespecularly reflected ray from the nominal surface.

The photo-sensitive element is a layered assembly where one layer is aphoto-sensitive layer and another layer is the retro-reflecting layer.

The element can be made thin enough to be used in film, as opposed toglass plate, applications.

When a lens is used to image the subject, the image may be positioned tobe in front of, on, or behind the photo-sensitive element. This resultsin a photograph where the image of the subject appears in front of, on,or behind the surface of the photograph.

The photograph may be viewed from either side by reflected light and thesubject appears as an orthoscopic or pseudoscopic view. The side awayfrom the viewer may be painted black.

Because the reflector that is used during exposure is an angularreflector, the photograph that results therefrom can be viewed withoutthe same disturbing surface reflections that obscure the viewing ofLippmann photographs. Thus, the utilization of the retro-reflector isone way to make a light-weight, thin, and flexible photograph, as theneed for the attachment of a thick, heavy, inflexible wedge is obviated.

By using the invention, a single 3-dimensional photograph may be madefrom 2-dimensional cross sections of 3-dimensional subjects. Here, thesame photo-sensitive element is exposed sequentially to photographs orto video display terminals, as examples, which represent cross sectionsof 3-dimensional subjects. During each of the multiple exposures, theimage of each cross section of the subject is optically positioned at adifferent distance from the photo-sensitive element. This can beaccomplished by varying the distances from the photo-sensitive elementto the lens, and the distance from the lens to the subject may remainfixed for all of the multiple exposures. This also can be accomplishedby varying the distances from the lens to the subject, and the distancefrom the lens to the photo-sensitive element may remain fixed for all ofthe multiple exposures. This also can be accomplished in other waysapparent to a person skilled in the art. The invention has particularapplication in medical imaging and in displaying seismic data.

The 3-dimensional photography of the invention is facilitated by the useof one or more multiple monochromatic light sources illuminating thesubject.

DEFINITIONS

As used in this specification and claims.

Light means electromagnetic radiation, unless visible light is specifiedin which case that portion of the electromagnetic spectrum withwavelengths from 400 to 700 nanometers is indicated.

Photo-sensitive is the same as light-sensitive.

The emulsion or emulsion layer is the same as the photo-sensitive layerin a layered photo-sensitive element; the layer which records the imageof the subject; the image carrying layer of a completed photograph. Theemulsion need not be in any technical sense a true emulsion.

A sheet is a broad, thin, often rectangular mass of any material; acoating on a surface.

A layer is a single thickness, coating or stratum spread out or coveringa surface; one sheet of a stack of 2 or more sheets wherein the sheetsare essentially parallel to one another.

Photography is the art or practice of producing an image of subjectsupon a photo-sensitive layer by the chemical action of light or otherradiant energy; the art of reproducing photographs from sensitivesubstances in permanent form.

A photographic system is one in which light is emitted from the subject,wherein some of said light from the subject falls upon a photo-sensitivemedium (or element) and is recorded (or made visible) by saidphoto-sensitive medium. The light from the subject may be reflectedlight from a light source or the subject may be self-luminous. An imageforming element may be located between the subject and thephoto-sensitive element.

An image, forming element is an element capable of forming (orcontributing to the formation of) an image of a subject. The image maybe real or virtual. The element may be a refractive element (a glasslens is an example) or it may be a reflective element (a concave metalmirror is an example). Holographic elements functioning as image formingelements are included.

A secularly reflecting surface is a like a common household mirror, apolished metal surface, or the shiny side of common household aluminumfoil. When a ray of light is incident on a specularly reflecting surfaceand at an angle to it, this angle is called the angle of incidence; theangle of reflection is equal to the angle of incidence. The reflectedray and the incident ray make an angle with respect to each other, orare not parallel (except in the trivial case of the incident ray beingperpendicular to the surface at which time the incident and reflectedrays coincide in position but are in opposite directions).

A retro-reflection layer is a layer, a surface, or a sheet, of materialthat reflects light in such a way that an incident ray is essentiallycoincident with the reflected ray; the incident ray and the reflectedray travel in opposite directions. FIG. 3 is a retro-reflecting layershowing a retro-reflecting layer 301, a light source 302, an incidentray 303, and the reflected ray 304 which is coincident with the incidentray 303 but in the opposite direction.

A photograph is an image of a subject produced by a photo-sensitivesheet.

If a photograph is a recording of the interference patterns of lightwaves that existed within the photo-sensitive layer during exposure, andif said interference patterns were due to incident light wavesinterfering with their reflections from a reflector that formed onelayer of a photo-sensitive element, and if viewing the image of thephotograph requires the interference of light waves, the photograph isan interference photograph.

A photo-sensitive layer is a layer, a sheet, or a surface that either isor contains light-sensitive material. A photo-sensitive element is alayered assembly wherein at least one of the layers is photo-sensitive.Silver halides and dichromated gelatin are common light-sensitivematerials. Other materials that are light sensitive and that can formphoto-sensitive layers are given within the publications under theheading "Related Publications." These and other less commonlight-sensitive materials that are useful in the invention arediscussed, along with requirements for exposing and processing, in thefollowing references:

(Collier. 1971) Collier, R. J., Burckhardt, C. B., and Lin, L. H.,Optical Holography, Academic Press, New York, 1971.

(Wolf, 1983) Wolf, E., et al., Progress in Optics Volume XX. NorthHolland, Amsterdam and New York, 1983.

(Goodman, 1990) Goodman, J. W., Ross, M., Erf, R. K., Korpel, A.,Starkweather, G. K., Laser Applications. Vol. 4. Academic Press, NewYork, 1980.

(Smith, 1977) Smith, H. M., Bartolini, R. A., Biedermann, K., Bordogna,D., Duncan, R. C. Jr., Keneman, S. A., Meyerhofer, D., Staebler, D. L.,Urbach, J. C., Holographic Recording Materials. Springer-Verlag Berlinand New York, 1977.

(Jeong, 1982) Jeong, T. H., Editor, Proceedings of the InternationalSymposium on display Holography. Holography Workshops, Lake ForestCollege, Lake Forest College, Lake Forest, Ill. 60045, July 12-16, 1982.

The terms "angular reflector," "angular reflector layer," and "angularreflecting layer" are defined under the heading "Definition of anAngular Reflector."

The term "non-angular reflector" is defined under the heading"Definition of a Non-Angular Reflector."

The term "retro-reflecting element" is defined under the heading"Definition of a Retro-Reflecting Element."

The term "retro-reflecting sheet" is defined under the heading"Definition of a Retro-Reflecting Sheet."

A retro-reflecting photo-sensitive element is a layered assembly whereinat least one of the layers is a photo-sensitive layer and wherein one ofthe layers is a retro-reflecting layer. FIG. 31 shows a retro-reflectingphoto-sensitive element 3101, wherein a photo-sensitive layer 3103, anda retro-reflecting layer 2801 is shown. Other layers may and may not bea part of the element. One of them can be the glue layer 3102. Otherlayers not shown, but that may be present, are an anti-reflecting layerand filter layers. Other layers could be added as would be readilyapparent to one skilled in the art.

A Lippmann photograph is a photograph that was made exactly (as far asis known) as Gabriel Lippmann made his photographs.

A Lippmann type photograph is a photograph that has at least some of itsfeatures (either as to how it was made or as to the properties of thecompleted photograph) like a "Lippmann photograph."

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section of a Lippmann light-sensitive element.

FIG. 2 is a cross section of a mat finish photograph showingreflections.

FIG. 3 is a cross section of a glossy finish photograph showingreflections.

FIG. 4 is a cross section of a Lippmann photograph showing reflections.

FIG. 5 is a cross section of a Lippmann photograph, with wedge attached,showing reflections.

FIG. 6 is a cross section of a photograph showing angular reflections.

FIG. 7 is a cross section of an angular reflector.

FIG. 8 is a cross section of a layered photo-sensitive element using anangular reflector.

FIG. 9 is a cross section of a non-angular reflector.

FIG. 10 is a cross section of another non-angular reflector.

FIG. 11 is a cross section of an angular reflector of metallic paint.

FIG. 12 is an enlargement of a portion of FIG. 11.

FIG. 13 is a cross section of an angular reflector of manysub-reflectors curved in shape.

FIG. 14 is a cross section of an angular reflector of manysub-reflectors flat in shape and with irregular slopes.

FIG. 15 is a cross section of an angular reflector of manysub-reflectors flat in shape and with regular slopes.

FIGS. 16, 17, 18, 19, and 20 are cross section of an angular reflectorthat are of parallel grooves of various shapes as indicated in thefigures.

FIG. 21 is a cross section of an angular reflector which is adiffraction grating.

FIGS. 22, 23, 24, and 25 are sub-reflectors that form a mosaic over asheet forming an angular reflector; their shapes are as shown in thefigures.

FIG. 26 shows a retro-reflecting element.

FIG. 27 shows a corner cube.

FIG. 28 shows a retro-reflecting sheet manufactured by the ReflexliteCorp.

FIG. 29 shows an improved retro-reflecting sheet.

FIG. 30 shows the improved retro-reflecting sheet of FIG. 29 used aspart of photo-sensitive element.

FIG. 31 shows the Reflexlite retro-reflecting sheet of FIG. 28 used aspart of photo-sensitive element.

FIG. 32 shows a grooved retro-reflector.

FIG. 33 is an axial view of a large lens useful in the 3-dimensionalphotography of the invention.

FIG. 34 shows a laser illumination system and diffuser.

FIG. 35 shows a laser illumination system and a moving diffuser.

FIG. 36 is omitted.

FIG. 37 shows a 3-dimensional photographic system that uses no lens.

FIGS. 38, 39, 40, and 41 show ways of viewing a 3-dimensional photographof the invention.

FIG. 42 shows a 3-dimensional photographic system that uses a lens.

FIG. 43 shows a 3-dimensional photographic system that uses a reflector.

FIG. 44 shows a 3-dimensional photographic system that converts a seriesof 2-dimensional cross sectional pictures of a 3-dimensional object intoa single 3-dimensional photograph.

FIG. 45 shows the Lippmann photo-sensitive element and reflections.

FIG. 46 shows an element of the image of a Lippmann photograph.

FIG. 47 shows the retro-reflecting photo-sensitive element of theinvention and reflections.

FIG. 48 shows an element of the image of the invention's photograph.

OBJECTS OF THE INVENTION

1. An object of the invention is to find a way of improving the Lippmannprocess of color photography, which produces a photograph with a2-dimensional image, to result in another process of color photography,which produces a photograph with a 3-dimensional image.

2. Another object of the invention is to find a way to make a camerathat takes colored 3-dimensional photographs, that employs theinterference of light waves, that where, during exposure, the distancebetween the camera and the subject can move more than one wavelength oflight, and where this is accomplished by changing the nature of thereflector used during exposure in the Lippmann process of colorphotography.

3. Another object of the invention is to find a photographic system thatmakes a 3-dimensional photograph from 2-dimensional cross sections of asubject by exposing a single photo-sensitive element sequentially toeach of the 2-dimensional cross sections and where, during eachexposure, the distance between the photo-sensitive element and thesubject (a 2-dimensional cross section) can move more than onewavelength of light.

4. Another object of the invention is to find a way to eliminate thethick, heavy, and inflexible wedge that is attached to the surface of acompleted Lippmann photograph (a 10 degree wedge suitable for covering a4×5 inch photograph can be 1/2 inch thick, weigh 1/2 pound, and isinflexible) and to accomplish this by changing the nature of thereflector used during exposure in the Lippmann process of colorphotography. This would result in a thin, flexible photograph suitablefor mounting in a conventional photograph album.

5. Another object of the invention is to find a way of convenientlyusing the same angular reflector to expose multiple photographs.

6. Another object of the invention is to find a way of making improvedangular reflectors for use in photo-sensitive elements.

7. Another object of the invention is to find a way of making animproved-retro-reflector for use in a photo-sensitive elements.

8. Another object of the invention is to improve the Lippmannphoto-sensitive element by using, instead of the specular reflector ofmercury, a diffraction grating.

9. Another object of the invention is to find a way of making a lens,that could be used with the photographic system of Item 2 (above),lighter in weight and smaller in size while preserving the horizontal3-dimensionality of the photographs.

10. Another object of the invention is to find a way of reducing thespeckle produced by a laser that is used to illuminate the subject, whenexposing a photo-sensitive element.

11. Another object of the invention is to find a transparent, watersoluble, thermoplastic glue, with a refractive index of about 1.5, witha softening temperature of less than 200 degrees F., that would beuseful as an index matching material or optical cement, and that wouldbe a useful material to use as a temporary glue for bonding together thelayers of a layered photo-sensitive element.

New Art Solutions to the Lippmann Photograph Viewing Problem

Non-Angular and Angular Relationships.

In FIG. 4, the direction of the surface reflection 405 and the imagereflection 408 are in the same direction; there is no angle betweenthem. Their relationship is non-angular. The view of the image isobscured by the surface reflection.

In FIG. 5, the direction of the surface reflection 505 and the imagereflection 508 are in different directions; there is an angle betweenthem. Their relationship is angular. The view of the image is notobscured by the surface reflection. This is what is wanted.

What is wanted, in conclusion, is a means of achieving an angularrelationship in the photograph between the image reflection and thesurface reflection.

An Improvement Over A Wedge.

Even though the attachment of a wedge to the completed photograph isbelieved by the inventor to be impractical, he knows of no other artprior to 1966 that achieves an angular relationship between the imagereflection and the surface reflection. The wedge is an attachment to thesurface of the photograph. It is attached after the photograph has beencompleted. Is there a different something that could be attached to thesurface of the completed photograph that would result in the desiredangular relationship between the image reflection and the surfacereflection but have none of the disadvantages of the wedge? Could thatsomething be thin, light weight, and flexible so that one could attachit to a Lippmann type photograph made on flexible film with a resultingphotograph that would be practical for mounting in a conventionalphotograph album?

Such an attachment was revealed in a patent application that was filedin 1966 (U.S. patent application Ser. No. 05/544,275). It is describedin U.S. Pat. No. 4,178,181 column 6, lines 27-33. The inventor has madean attachment of transparent material of parallel grooves, similar incross section to that shown in FIG. 7, and attached it to a Lippmanntype photograph and it works.

Is There A Better Way?

It would be very neat if it was possible to require nothing to beattached to the completed photograph in order to achieve an angularrelationship between the image and surface reflections. In other words,could the need for a wedge or wedge substitute be completely obviated?The previous discussion describes something that is done to thephotograph the photograph is made, not something that is done during themaking of the photograph. Could the photo-sensitive element be made insuch a way that the resulting photograph would reflect the imagereflection in one direction and the surface reflection in anotherdirection?

Is there a way, during exposure, of using some kind of reflector otherthan the specular reflector used by Lippmann? He used a single, planar,specularly reflecting surface (of liquid mercury).

The desired result would be achieved in the photograph if the reflectorthat was used during exposure was such that the patterns of parallel,partially reflecting planes, that form the image of the resultingphotograph, were at an angle to the surface of the photograph. Thisdesirable condition is shown in FIG. 6 that shows the photograph 601 anda small portion of the photograph 602 containing patterns of parallel,partially reflecting planes, that form the image of the completedphotograph, and that are at an angle to the surface of the completedphotograph. Also shown are a light source 603, an incident light ray604, the specular reflection from the surface 605, and the specularreflection from the image beneath the surface 606. When the viewerobserves the photograph from 607, the specular surface reflection 605 isnot seen.

The inventor knows of no art prior to 1966 that points out thedesirability of such a result nor a photo-sensitive element thatproduces such a result.

A Discovery is Made

It was discovered that an "angular reflector," used as part of thephoto-sensitive element during exposure, produces the desired resultthat is: (1) a photograph that requires the attachment of neither awedge nor a wedge substitute to the surface of the completed photographin order to view the image reflection without being obscured by thesurface reflection. (2) a photograph that is thin, light weight, andflexible, and therefore suitable for mounting in a conventionalphotograph album. The above referenced patent application filed in 1966(Ser. No. 05/544,275) provided various designs for angular reflectors.

Definition of An "Angular Reflector."

An "angular reflector" is a reflecting sheet that reflects light at anangle to a specularly reflected ray from the nominal surface. FIG. 7shows an angular reflector. The reflector 701 and sub-reflectors 702 areshown that are at an angle to the nominal surface 703. An Incident ray704, the specularly reflected ray 705 from the nominal surface 703, thereflected ray (or light) 706 from the angular reflector 701, the angle707, between the light 706 reflected by the reflector 701 and thespecularly reflected ray 705 from the nominal surface 703, is alsoshown. This reflector 701 is an angular reflector because it reflectslight 706 at an angle 707 to the specularly reflected ray 705 from thenominal surface 703. The nominal surface of the reflector is a referenceplane useful in describing the angularity of light rays; it is alwaysparallel to the photo-sensitive layer, or layers, when the angularreflector is part of a layered photo-sensitive element. However, theremay be other layers between the reflector and the photo-sensitive layer;as an example, a glue layer commonly attaches the reflecting layer tothe photo-sensitive layer.

When an angular reflector is a layer of a layered photo-sensitiveelement, it is designated as the angular reflector, or the angularreflector layer, or the angular reflecting layer.

An index matching material with a refractive index of about 11/2 usuallyfills the space between the sub-reflecting surfaces and the nominalsurface and it may be a liquid, solid, or a semi-solid.

When the angular reflector of FIG. 7 is used as part of a layeredphoto-sensitive element, FIG. 8 results. It shows the photo-sensitiveelement 801, the angular reflector 701 with its sub-reflecting surfaces702, the photo-sensitive layer 802, the photo-sensitive layer support803, index matching material 804 that fills the space between thesurface of the reflector (or the sub-reflecting surfaces) and thephoto-sensitive layer, and an exposing ray 805. FIG. 8 may be comparedto FIG. 1.

Some Angular Reflectors.

Reflectors made up of sub-reflectors with part or all of their surfacesat an angle to the nominal surface are angular reflectors. A diffractiongrating used as a reflector is an angular reflector. A layer of paintwith reflective metallic pigment particles is an angular reflector. Aretro-reflecting sheet is an angular reflectorA diffuse surface, as thedull side of common household aluminum foil, is an angular reflector.

The effect of using an "angular reflector," as part of thephoto-sensitive element during exposure, is that the patterns ofparallel, partially reflecting planes, that form the image of theresulting photograph, are at an angle to the surface of the photograph;this has the desirable consequence of producing a photograph where theimage reflection is in one direction and the surface rejection is inanother direction (see FIG. 6).

An "angular reflector" that has been made and successfully used by theinventor as part of a photo-sensitive element is shown in FIG. 7. Theangular reflector is a sheet where the surface is covered with straightparallel grooves with a sawtooth cross section. FIG. 7 shows thereflector 701, the sub-reflector surfaces 702 that are metalized andspecularly reflecting, the groove spacing 708 that is 0.001 inch, thenominal surface 703, and the angle 709 between the sub-reflectorsurfaces 702 and the nominal surface of the reflector 703, which isabout 6 degrees.

FIGS. 4a, 4b, and 4c, of U.S. Pat. No. 4,178,181 show "angularreflectors" and they are described in the specification. The terms"angular reflector" and "sub-reflectors" are not used in thespecification of U.S. Pat. No. 4,178.181.

Definition of A "Non-angular Reflector.

A "non-angular reflector" is a reflector that does not reflect light atan angle to a specularly reflected ray from the nominal surface. Thereflected light from the reflector and the specularly reflected ray fromthe nominal surface are in the same direction.

Some Non-Angular Reflectors.

The Lippmann reflector is "non-angular" in that it is a reflector thatdoes not reflect light at an angle to a specularly reflected ray fromthe nominal surface. The reflecting surface is indeed the nominalsurface. Thus, the light reflected from the reflector and the nominalsurface is one and the same. FIG. 9 show a Lippmann reflector 901, thereflecting surface and nominal surface 904, an incident light ray 902,and specularly reflected ray 903 from the nominal surface and from themercury surface 904. The razor used by Lippmann (liquid mercury) takesthe form of the surface against which the mercury rests, which is theemulsion surface, and the emulsion surface is a specular reflector.

Another "non-angular" reflector is shown in FIG. 10 where the reflector1001, the sub-reflecting surfaces 1002, and the nominal surface 1003 areshown. An incident light ray 1004, light reflected from the reflector1005, and the specularly reflected ray 1006 from the nominal surface1003 are shown. The light 1005 reflected from the reflector 1001 is inthe same direction as the light ray 1006 reflected from the nominalsurface 1003. They do not make an angle with one another. This is a"non-angular" reflector (it is a reflector that does not reflect lightat an angle to a specularly reflected ray from the nominal surface).

Angular Reflector, an Improvement over Non-Angular Reflector

A Better Solution, 1966 Patent Application.

A better solution (than the wedge or a wedge substitute) makes the imageof a Lippmann type photograph viewable without being obscured by thesurface reflection; It was revealed in the 1966 patent application whichresulted in U.S. Pat. No. 4,178,181. The solution was to use, duringexposure (instead of the non-angular reflector of prior art and used byLippmann, which was a single, plane, specularly reflecting surface), anangular reflector that is made up of a multiplicity of tinysub-reflecting surfaces that are rounded bumps, flat or irregularsurfaces, or paint particles; the sub-reflector surfaces are angled withrespect to the reflector's nominal surface. These small sub-reflectingsurfaces that are rounded or flat are described in U.S. Pat. No.4,178,181, column 6, lines 38 through column 7 line 2, and are shown inFIGS. 4a, 4b, and 4c. These are "angular reflectors" although notdescribed by the term "angular reflector" in the patent. They havesub-reflecting surfaces that are at an angle to the nominal surface ofthe reflector. Each of these reflectors is an angular reflector inasmuchas each is a reflecting sheet that reflects light at an angle to aspecularly reflected ray from the nominal surface.

These tiny rounded or flat sub-reflecting surfaces may beheterogeneously oriented, as in aluminum particles in paint (see FIG.4c, U.S. Pat. No. 4,178,181), or may be orderly and repetitious as toslope, position, and curvature, when seen in a cross section of thereflecting surface (see FIG. 4a and 4b, U.S. Pat. No. 4,178,181).

It would be expected that certain shape and arrangement configurationswould be better than others from functional considerations and from easeof fabrication considerations. There is a large number of configurationsthat would be described as being "angular reflectors."

Heterogeneous Reflector Advantages.

(The surfaces of the sub-reflectors are heterogeneously oriented.) Theadvantage is that it produces a photograph that is easy to view withrespect to the positioning of the light source, photograph, and eye.However, the brightness of the image is not very bright (as compared toa patterned reflector). An example of a heterogeneous reflector is touse paint, as described in U.S. Pat. No. 4,178,181 column 6 line 49through column 7, line 2. This has been used by inventor successfully inmaking a photograph. Another heterogeneous reflector is the diffuse sideof common household aluminum foil.

Patterned Reflector Advantages.

The advantage is that it can produce a very bright image but thepositioning of the light source, photograph, and eye can be verycritical. By referring to U.S. Pat. No. 4,178,181, FIG. 4a, one can seea pattern in the sub-reflecting surfaces that is a repetition oralternating slopes and where the alternating slopes make essentiallyequal angles with the nominal surface of the reflector. FIG. 4b (of U.S.Pat. No. 4,178,181) suggests a repetition of alternating slopes wherethe alternating slope make unequal angles with the nominal surface ofthe reflector. The inventor has used a reflector (shown in FIG. 7)madewith equal alternating slopes where the alternating slopes make angles(with the nominal surface of the reflector) of 6 and 84 degrees; the 6degree angle is shown at 709. This patterned reflector is of straightparallel grooves on a planar surface and the grooves 708 are spaced0.001 inch apart; the reflecting surface is metal. It works. It was madeby Fresnel Optic, 1300 Mt. Read Blvd., Rochester, N.Y. 14606.

Combination Reflector Advantages.

A combination of a heterogeneous reflector and a patterned reflector hasbenefits. One that was tried was where (the above described) groovedreflector was of plastic (acrylic or Plexiglas) that had an aluminizedreflecting surface (by vacuum deposition). The result was a reflector inwhich one could see one's own image, except at an angle to theperpendicular to the general plane of the reflector. (In ordinaryspecular reflectors or mirrors, one can, of course, see one's own imageexcept it is perpendicular to the general plane of the reflector.) Asolvent for the plastic (chlorobenzene) was allowed to come into contactwith the reflector, with the result that the small angled reflectingsurfaces were degraded, so that the reflections therefrom becameslightly diffused. The length of time in the solvent determines thedegree of degradation. Alternately, the reflector could have been madeby degrading the groove surfaces first with solvent, and thenaluminizing them. The result was that the reflection from the image wasstill very bright but the positioning of the light source, photograph,and eye was less critical than before.

Flexibility of Photographs Made Possible by Using Angular ReflectorDuring Exposure

The invention (of using an angular reflector during exposure) makesLippmann type photographs possible that are flexible. The inflexibilityof the Lippmann photograph-wedge combination, of prior art, was aconsequence of the necessity of using the wedge. The wedge wasnecessitated as a consequence of the properties of the photograph, dueto the reflector that was used during exposure; it was a non-angularreflector. It was a single, plane, specularly reflecting surface.

The invention changes the nature of the reflector used during exposurefrom a non-angular reflector that was a single, plane, specularlyreflecting surface, to an angular reflector that is a reflecting sheetthat reflects light at an angle to a specularly reflected ray from thenominal surface. An angular reflector is provided by a multiplicity oftiny sub-reflecting surfaces that are rounded bumps, flat or irregularsurfaces, or are paint particles; their surfaces are angled with respectto the nominal reflecting surface. See U.S. Pat. No. 4,178,181 column 6,line 38 through column 7, line 2, and FIGS. 4a. 4b, and 4c. Also, column3, lines 12-19 are of interest. The nature of the photograph thatresulted was changed so that an inflexible wedge was no longernecessitated and a flexible photograph (as made on thin flexible filminstead of glass plate) was made possible. Thus, the use of an angledreflector is a means of facilitating the making of a flexible Lippmanntype photograph.

As known by inventor, viewable, Lippmann type photographs that wereflexible did not exist prior to 1966.

With the invention, viewable, thin, light weight, flexible, Lippmanntype photographs suitable for mounting in a conventional photographalbum can be, and have been, made by the inventor. The images are moreeasily seen when the positioning of the illumination source, the viewer,and the photograph is optimized.

Ways of Making Angular Reflectors Angular Reflectors Can Be Made in aVariety of Ways.

Metallic Paint.

One way that an angular reflector can be made is by the use of metalpowder in a paint, as by using aluminum powder. The aluminum paint maybe applied to the surface of the photo-sensitive layer. The paint layeris an angular reflector because it satisfies the definition of anangular reflector; the paint layer is a reflecting sheet that reflectslight at a variety of angles to a specularly reflected ray from thenominal surface. The paint layer is a sheet; it is of manysub-reflectors; the surfaces of the metallic aluminum particles in thepaint are many sub-reflectors and most of the reflecting surfaces of thesub-reflectors are at an angle to the nominal surface. FIG. 11 shows aphoto-sensitive element 1101, the angular reflection 1102, the nominalsurface 1103, the photo-sensitive layer (emulsion layer) 1104, thephoto-sensitive layer support 1105, a ray of exposing light 1106, themany sub-reflectors 1107 (metallic pigment particles), and thetransparent vehicle 1108. The surfaces of the sub-reflectors (paintparticles) that are of importance in reflecting light are the surfacesof said sub-reflectors that are toward the nominal surface; only theones closest to the nominal surface are effective because they cast ashadow on the surfaces farther away from the nominal surface. FIG. 12shows an enlargement of a portion of FIG. 11 and shows one paintparticle 1201, the nominal surface 1202 (the vehicle is not shown), anexposing ray 1203, the specularly reflected ray 1205 from the nominalsurface 1202, and the reflected light 1207; It can be seen thatreflected light 1207 is at an angle to the specularly reflected ray1205. Similarly, It can be seen that exposing ray 1204 results in aspecularly reflected ray 1206 from the nominal surface 1202, and thatpart of the exposing ray penetrates the nominal surface 1202, strikesthe paint particle 1201 and is reflected thereby resulting in ray 1208which is at an angle to the specularly reflected ray 1206. An angularreflector in the form of a paint is shown in U.S. Pat No. 4,178,181,FIG. 4c.

Foil.

Another angular reflector can be made by the use of a foil or a deformedmetal surface where its surface is formed into a multiplicity ofreflecting surfaces. Tiny rounded bumps, or flat or irregular shapes canform the sub-reflecting surfaces. Angular reflectors in the form or afoil with various shapes of sub-reflectors is shown in U.S. Pat. No.4,178,181, FIGS. 4a and 4b. These reflectors are angular reflectorsbecause each satisfies the definition of an angular reflector. Thepattern sheets used in metal etchings may also be used angularreflectors; they are angular reflectors because they satisfy thedefinition of an angular reflector. There are many types of angularreflecting surfaces present on metal etching sheet #T55, supplied byDufex Prints, F. J. Warren, Ltd., Hitchin Herts, England. This companycan make entire sheets or the patterns shown on Sheet #T55 or on otherpatterned sheets they supply as T23, T25, T26, T27, T30, T31, T39, T40,T41, T51, T52, T55, also Ref. Numbers 183,770 Product code 80342, andRef. Numbers 200,033, 200,067, 200,066 and others. Lenticular Sheeting,as once supplied by Edmund Scientific Co. of Barrington, N.J. can alsobe used as an angular reflector provided the surface that is patternedis metallized; one side of the sheet is flat and the other is bumpy withvery small lenses. The bumpy side is aluminized and the resultingangular reflector may be used with either side toward thephoto-sensitive layer, although the bumpy side toward thephoto-sensitive layer is the preferred orientation.

Sub-Reflectors Curved in Shape.

The reflector resulting from many sub-reflectors curved in shape is anangular reflector because it fits the definition of an angularreflector. FIG. 13 shows the nominal surface 1301 of a reflector withsub-reflectors 1302 that are rounded in shape. The direction of thelight to be reflected is shown at 1303.

Sub-Reflectors Flat in Shape, Irregular in Slope.

The reflector resulting from many sub-reflectors flat in shape and withirregular slopes is an angular reflector because it fits the definitionof an angular reflector. FIG. 14 shows the nominal surface 1401 of areflector with sub-reflectors 1402 flat in shape and with irregularslopes. The direction of the light to be reflected is shown at 1403.

Sub-Reflectors Flat in Shape, Regular in Slope.

The reflector resulting from many sub-reflectors flat in shape and withregular slopes is an angular reflector because it fits the definition ofan angular reflector. FIG. 15 shows the nominal surface 1501 of areflector with sub-reflectors 1502 flat in shape and with regularslopes. The direction of the light to be reflected is shown at 1503. Thedimension 1504 may be 0.001 inch.

Characteristics of Different Shapes.

It is to be expected that certain shapes, sizes and slopes are to bemore useful than others. The inventor has had a reflector of thedescription of FIG. 15 made by diamond machining and found it useful.The material of the reflecting surface is evaporated aluminum onto anacrylic base of the desired form. The many angular surfaces of thesub-reflectors form a patterned surface. The pattern is of straightparallel grooves across a nominal surface that is a reflector; it isessentially planar. The shapes of the sub-reflectors form a patternacross the nominal surface if a theme is repeated.

Straight Grooves.

The pattern of FIG. 7, when physically made as above and used duringexposure to expose the photosensitive element, produces a photographwith an image that is particularly bright. When the photograph is viewedby using the sun to illuminate the photograph, the reflection from theimage is so bright that it is blinding (this is the reflection from theimage, not the reflection from the surface of the photograph). At thesame time, the position of the viewer, photograph, and light source(sun) are very critical; either the reflection from the image is toobright, or the image cannot be seen at all. In order to make the viewingless critical, and at the same time retain a degree of brightness, onefactor may be traded off for another. The image may be made less bright,but the viewing angle range may be increased. This can be accomplishedby rounding the sub-reflector's angled surface 702 of FIG. 7 so thatpatterns indicated by FIG. 16 or 17 result. The pattern of FIG. 18 canalso be used. The design of FIG. 16 is preferred.

Another reflector of interest, which has straight parallel groovesacross a planar surface, is shown in FIG. 19 which shows the nominalsurface 1901 and sub-reflecting surfaces 1903 and 1904 which alternatelyslope in different directions; they may make angles 1902 of 30 degreeswith the nominal surface 1901. They may also make angles of 10 or 20degrees (etc) with the nominal surface 1901. In many applications,angles of no more than 20 degrees (for angle 1902) are desirable. Inother applications, angles of 30 degrees are desirable.

Another reflector of utility, which has straight parallel grooves acrossa planar surface, is shown in FIG. 20 which shows the nominal surface2001 and sub-reflecting surfaces 2002 and 2003. The pattern is repeated.Sub-reflecting surfaces 2003 may be (and may not be) parallel to thenominal surface 2001 but surfaces 2002 are at an angle to the nominalsurface 2001. The projected distance of the steeper sub-reflectingsurfaces 2002 is 2005. The projected distance of the less steepsub-reflecting surfaces 2003 is 2004. The ratio of the projecteddistances 2004 and 2005 can vary from 1 to 100 or 100 to 1. However, thebest mode contemplated by inventor is a ratio of 1 to 1. When thesurfaces 2003 are parallel to the nominal surface 2001, this reflectorcan be considered to be a composite of an angular reflector (made up ofall angular components 2002) and a non-angular reflector (made up of allnon-angular components 2003).

Diffraction Grating.

A diffraction grating, of straight (or curved) parallel grooves, isanother form of an angular reflector, and is of utility. There are 3diffraction grating types that are of particular interest. In the first,the grating should be made so that the positive first order ismaximized; all other orders are suppressed. In the second, the gratingshould be made so that the positive first order and the zero order aremaximized (they should be about equal). In the third, the grating shouldbe made so that the positive and negative first order spectra aremaximized and all other orders are suppressed. The preferred directionof the grooves is vertical (as opposed to horizontal) when used in acamera. There are on the order of 25,000 lines per inch or the linespacing is on the order of 0.000,040 inch FIG. 21 depicts a diffractiongrating where the nominal surface 2101, zero order reflection (specularreflection from the nominal surface) 2102, first order positive spectra2103, the first order negative spectra 2104, and the incident ray 2105are shown. In FIG. 21 it can be seen that reflected light 2103 and 2104is at an angle to the specularly reflected ray 2102 from the nominalsurface 2101.

Diffraction and Reflection Compared.

The groove spacing of FIGS. 7, 8, 13, 15, 16, 17, 18, 19, and 20, canvary between 0.010 and 0.0002 inch, for common photographic work, andthe primary cause of the reflection is by reflection (rather than bydiffraction and refraction) from the surfaces of the sub-reflectors. Thepreferred spacing is 0.001 inch. A company that can make this type ofreflector is the Fresnel Co. of Rochester. N.Y.

The groove spacing of the diffraction gratings shown in FIG. 21 can varybetween 0.000,2 to 0.000,010 inch for common photographic work, and theprimary cause of the reflections 2103 and 2104 is by diffraction andrefraction (rather than by reflection) from the sub-reflectors, which inthis case are grooves. The preferred spacing is 0.000,040 inch.Diffraction grating sheeting that can be used for this purpose isavailable from Steve McGrew, Light Impressions, Inc., in Ben Lomand,Calif.

Mosaics.

The sub-reflectors may form a mosaic over the reflecting sheet. Thereflecting sheet may be covered with individual pieces, orsub-reflectors, which make up the mosaic, that are outlined in a squareor rectangular shape. They may also be outlined in a hexagonal shape asused in foundation for the wax honeycombs of honey bees. Other shapes orpurposeful designs are also possible. The size of the individual mosaicpieces, (or sub-reflectors) as used in ordinary photography, is 0.020 to0.0002 inch across with 0.002 inch across as the preferred size,although from cost considerations, lager mosaic pieces (orsub-reflectors) may be more desirable. The curved surfaces of thesub-reflectors are polished for high reflectance. Usually, the entirereflecting surface is covered with thousands of identically shapedindividual pieces, and if they have an orientation, they are oriented inthe same direction. Some of the sub-reflector (or individual mosaic)designs that are possible are shown in FIGS. 22, 23, 24, and 25. FIG. 22is described as a pillow design, or convex surface. FIG. 23 is describedas a tilted pillow design, or tilted convex surface. FIG. 24 isdescribed as a concave surface design. FIG. 25 is described as a tiltedconcave surface design. The preferred design is shown in FIG. 23, thetilted convex design.

Size of Sub-Reflectors.

The outline of the sub-reflectors can be visible in the completedphotograph. Thus, the size of the sub-reflectors should be small enoughto be not resolved by the eye when viewing the photograph. In selectingthe size of the sub-reflectors, one must consider the distance fromwhich the photograph will be viewed and the fineness or the coarsenessof the detail in the subject photographed. For example, If the subjectbeing photographed is a large red dot on a black wall, sub-reflectorsthat are quite large may be very adequate, assuming the prime point ofinterest is the presence or absence of the red dot in the photograph.If, however, the subject being photographed is a web being spun by aspider, sub-reflectors that are quite small are required. Thus, thesub-reflector size should be small compared to the detail of the imagein the photograph.

Benefits of Angular over Non-Angular Reflectors

An advantage that results from using angular reflectors during exposure,instead of using non-angular reflectors during exposure, is that it ismuch easier to see the image in the interference photograph thatresults. Prior art required that a wedge of glass be attached to thesurface of the completed Lippmann photograph in order to make the imageeasily. With this wedge attached, it was impossible to make a thinLippmann photograph that was light in weight and thin enough to beflexible. By the use of the reflectors shown and suggested by the above,during exposure, photographs result that are suitable for placing in aphotograph album that are thin, light weight, and flexible.

Firsts of the 1966 Patent Application

The invention provides following results, as far as is known by theinventor:

1. The first practical way to make a viewable Lippmann type photographwhere the image of the photograph can be easily viewed without a thick,heavy wedge being attached. This is a consequence of using an angularreflector during exposure. Prior art used a non-angular reflector duringexposure.

2. The first practical way to make a viewable Lippmann type photographwhere the photograph is thin enough and flexible enough that it can bemounted in a conventional photograph album. This, too, is a consequenceof using an angular reflector during exposure. Prior art used anon-angular reflector during exposure.

3. From a historical position, U.S. Pat. No. 4,178,181 gives the firststatement in the literature that specifies the use of flat,photo-sensitive grains as a means of increasing the sensitivity of anyphoto-sensitive element.

The inventor believes that photographic film made with flat,photo-sensitive grains, according to the specification, and used ininterference photography (Lippmann type photography) possessessensitivity and other advantages that are so beneficial that the use ofthe film in ordinary photography would be automatically considered by aperson skilled in the art. Flat grains are not new. Several referenceshave to do with making flat grains and give details as to size andthickness; none of them suggest utilizing grain of about 50 nanometersor less in thickness nor do they suggest any benefit in doing so.However, once the benefits of using grains of about 50 nanometers orless has been revealed, as has the inventor in the 1966 application, aperson skilled in the art can use the information in the prior artreferences for obtaining the grain of the desired dimensions byextension of the techniques that were used by prior workers in makingflat grains.

A Discovery that Makes 3-D Photographs Possible

There has been discovered a certain kind of angular reflector that hasbeen used in place of the non-angular reflector that Lippmann used. TheLippmann process of color photography results in 2-dimensionalphotographs. With the use of a certain kind of angular reflector inplace of the non-angular reflector of the Lippmann process, a newprocess of color photography results. The result of the new process isthat 3-dimensional colored photographs result. A certain kind of angularreflector has been discovered that results in a 3-dimensionalphotograph; it is a reflector covered with retro-reflecting elements.

A Comparison of 2-D and 3-D Photographs

A comparison of 2-dimensional photographs and 3-dimensional photographsis of interest. The image carrying (emulsion) layer of both is as thinor thinner than a common sheet of newspaper. When a 2-dimensionalphotograph is viewed, the image appears on the 2-dimensional plane ofthe photograph. When a 3-dimensional photograph is viewed, the image canappear in front of, on, or behind, the 2-dimensional plane of thephotograph by some distance, as many inches.

Definition of a Retro-Reflecting Element

A retro-reflecting element is defined as a mass of material that has theproperty of returning an incident ray of light essentially along theincident light path, but in the opposite direction. (Their paths areparallel, and in opposite directions, but may be offset slightly fromone another.) FIG. 26 shows a retro-reflecting element 2601, with theincident light ray 2602, and the reflected light ray 2603 that is alongthe incident light path, but in the opposite direction

Definition of a Retro-Reflecting Sheet

A retro-reflecting sheet is defined as a sheet of material that has theproperty of returning an incident ray of light essentially along theincident light path, but in the opposite direction; the incident ray offight may fall anywhere on the surface and at any angle from 0 to 90degrees from the perpendicular to the surface. The retro-reflectingsheet may be made up of retro-reflecting elements. If the light beamfrom a flashlight is directed to any position on this sheet, and at anyangle, the light beam is reflected back to the flashlight.

Differences Between a Retro-Reflecting Sheet and a Common Reflector Make3-D Photographs Possible

It is this property (of reflecting light back on itself) of aretro-reflecting sheet (or layer) that makes the 3-dimensional processwork, the same things that were just said about a retro-reflecting sheetcannot be said about an ordinary reflecting surface, as provided by acommon household mirror or the mirror formed by a layer or mercuryagainst the specular surface of glass (which is a specular surface) orthe specular surface of the emulsion layer of a photo-sensitive element.In other words, if we now consider a common household mirror, and thebeam of a flashlight is directed to any position on this surface, andfrom any angle, the light beam is not reflected back to the flashlight(except in the trivial case when the flashlight beam is perpendicular tothe plane of the mirror). It is the property of a retro-reflector toreflect light in a desirably different way than light is reflected froman ordinary mirror that enables it to produce a 3-dimensionalphotograph.

Kinds of Retro-Reflecting Elements

What kind of things form a retro-reflecting element? A crystal oflithium niobate is a retro-reflecting element. A crystal of bariumtitanate is a retro-reflecting element. A clear glass bead reflector isa retro-reflecting element. A cube-corner reflector is aretro-reflecting element.

Lithium Niobate. Barium Titanate.

A sheet or flat section of a crystal of lithium niobate (or the like, asbarium titanate) can form a layer or a mosaic of many pieces can form alayer. Flat pieces of such a crystal can be formed by sawing, cleaving,or by making thin sections of the material by the process by which thinsections of mineral specimens are made for petrographic studies.

Glass Beads.

Glass beads are perhaps the most common kind of retro-reflectingelements and are used extensively for road markers in lane dividingpaints and reflective signs that light-up when the headlights of anautomobile shine on them at night. Sheeting with glass beads coveringthe surface is manufactured by the 3M Company under the trademark"Scotchlight®".

Cube Corners

An example of a cube-corner reflector is an upper ceiling corner of aroom where rectangular mirrors cover the three intersecting surfaces.The property of this reflector is that a person located anywhere in theroom may look up into the corner and the person sees his face imaged inthe corner. If a flashlight is directed into this corner from anywherein the room, the light is reflected from this corner back to theflashlight.

FIG. 27 shows a cube-corner piece 2701 cut from a cubical box 2702. Thepoint of the cube-corner is 2703. FIG. 28 shows a retro-reflectingsheet. A transparent sheet 2801 is shown with many cube-corners 2802protruding. The cube-corners 2802 have the point of the cornersindicated by 2803. The surfaces of the cube-corners 2802 may bemetalized to provide desired reflectivity and are covered withprotective paint 2807. When a ray of incident light 2804 is now directedanywhere on the nominal surface 2805, the incident light 2804 isreflected by the cube-corner reflectors 2802 essentially back along thesame path as the incident light ray 2804; the reflected ray is 2806.Light is internally reflected by the surfaces of the cube corners 2802.The reflector is made up of sub-reflectors 2802.

Utilizing the properties of cube-corner reflectors, the Reflexlite Corp.of New Britain, Conn., makes retro-reflecting sheets of thin plasticwhere the cube-corner reflectors are very small; there are 47,000corners per square inch. The cube corners are protrusions from thesurface 2805. The Reflexlite material is used in applications similar tothe applications found for sheets of glass beaded material, as producedby 3M. The Reflexlite material is depicted in FIG. 28. The thickness2808 is about 0.010 inch, including the protective paint The onlyretro-reflective sheeting that Reflexlite supplies is as shown in FIG.28. In the applications for which the Reflexlite material is intended,the distance between the nominal surface 2805 and the reflecting surface2809 is of no consequence. However, for this photographic application,as a retro-reflecting layer that is part of a photo-sensitive element,another consideration is of great importance. For this photographicapplication, it is desirable to have the corner cube sub-reflectors asclose to the photo-sensitive layer as possible, or the distance 2810should be a minimum.

An Improved Cube Corner Retro-reflector Design

FIG. 29 shows an improved retro-reflector design that is better than theReflexlite product, as shown in FIG. 28, for this photographicapplication. Here, the cube corner reflectors 2902 are depressions inthe nominal surface 2903 of the improved retro-reflector 2901 that istoward the photo-sensitive layer. The points 2904 or the corner cubesare shown. The surfaces 2902 of the retro-reflector are metallized toenhance reflectivity. Protective paint is unnecessary as the cubecorners are protected, being depressions rather than being protrusionsas is the case for the Reflexlite material. Index matching material, asmelted fructose, fills the depressions of the improved retro-reflectorand can glue this reflector to the photo-sensitive layer of aphoto-sensitive element.

FIG. 30 shows this Improved retro-reflector 2901 as part of aphoto-sensitive element 3001. The index matching glue 3002, thephoto-sensitive layer 3003, and the photo-sensitive layer support 3004are also shown. The drawing shows substantial thickness of the indexmatching glue 3002 that is located between the nominal surface 2903 ofthe retro-reflector 2901 and the surface of the photo-sensitive layer3003; in practice, this is minimized and is easily made less than 0.001inch thick; no finite thickness is required. This works better than theReflexlite product. Thus, its use facilitates the making of an improvedretro-reflecting photo-sensitive element.

The advantages of the improved retro-reflector photo-sensitive elementcan be appreciated by reference to FIG. 31 which shows the Reflexliteretro-reflector 2801, as part of a photo-sensitive element 3101 beingexposed to light 3106 from only one side of the element. The Indexmatching glue 3202, the photo-sensitive layer 3103, and thephoto-sensitive layer support 3104 are also shown. In contrast to theelement 3001, the thickness between the nominal surface 3105 of theReflexlite retro-reflector and the surface of the photo-sensitive layer3103 cannot be made less than the thickness 2810 of FIG. 28 (which is0.0075 inch thick) because this is the thickness of the available priorart material (element 2801) and prior art describes no advantage ofmaking it thinner. Finite thickness of 2810 is required as thisthickness is support for the cube corners 2802.

Tooling for the retro-reflector described above and shown in FIG. 29 canbe made by Fresnel Optics, of Rochester, N.Y.

A Grooved Retro-Reflector

A second choice is available for the configuration of theretro-reflecting layer, and this is a "grooved retro-reflecting" layer.It is a somewhat common experience to encounter mirrors covering 2 wallsthat intersect in a corner of the room. When one looks into the cornerfrom any place in the room, one sees one's own image, and the image islocated at a position that is on the same level as the viewer's eyes (oris on a plane that is perpendicular to both mirrors, which intersect atright angles). A grooved retro-reflecting sheet (to be used as a layerof a retro-reflecting photo-sensitive element) can be made to accomplisha similar thing. Parallel grooves are made into a sheet and adjacentgroove sides make 90 degree angles with one another. The 3-dimensionalphotograph that results has horizontal 3-dimensionality but not vertical3-dimensionality.

This kind of grooved retro-reflector can be made to be used with thehorizontally elongated lens or a photographic system used to take3-dimensional photographs. The grooves could be made on 0.001 inchspacings. The preferred direction or the grooves is vertical when takinga picture of a person with the camera oriented in the common way. Acompany capable of making this kind of a reflector is Fresnel Optics ofRochester, N.Y. The system that results produces photographs that arehorizontally 3-dimensional and does so with a camera that is efficientin both size and weight. FIG. 32 shows a grooved retro-reflector 3201where the sides of the grooves 3202, which are planar, make equal angles3203 with the nominal surface 3204. The angle 3205 is essentially 90degrees.

Another angular reflector design of advantage is also adequatelydepicted by FIG. 32, but this time it is not a retro-reflector as thereflected ray is intentionally made to be at an angle to the incidentray. The purpose is to make illumination of the resulting photographeasier. The angle 3205 is purposely made larger or smaller than 90degrees, but an angle larger than 90 degrees is preferred. Angle 3205can vary between 90 and 112 degrees while keeping angles 3203 equal.

Prior Art: Scenery for Background Produced inStudio by Use ofRetro-reflecting Sheet.

The 3M glass beaded material has been used in a photographicapplication. This application is one of studio photography. It is usedfor producing background scenery from a slide projector. A wall behindthe subject is covered with the retro-reflecting sheeting. A slideprojector, aimed vertically at a beam splitter, projects a scene, thatis to be the background, on the wall covered with the retro-reflectingmaterial. A camera is aimed horizontally at the beam splitter and at thebackground scene that is reflected back to the beam splitter by theretro-reflecting sheet on the wall. The subject to be photographed isplaced between the beam splitter and the wall covered by theretro-reflector. The subject is lighted by overhead lights. Because thelight from the background is very bright due to the retro-reflectingsheet being a very good reflector and because the subject masks theretro-reflecting sheet, the photograph that results shows the subjectsurrounded by the desired background. This photographic use ofretro-reflecting sheeting has nothing to do with a system that producesa photograph with a 3-dimensional image nor anything to do with alayered photo-sensitive element that includes a reflector as part of thephoto-sensitive element. The photograph that is produced is in everysense a 2-dimensional photograph.

How to Make a Retro-Reflecting, Photo-Sensitive Element

A retro-reflecting photo-sensitive element can be made by glueing asheet of suitable film and a retro-reflecting sheet together.

A sheet of 8E75 Agfa-Gevaert film is suitable. A retro-reflecting sheetof product designated as A/C 1000, or similar, available from ReflexliteCorp. of New Britain, Conn. is suitable. The polycarbonate option ispreferred over the acrylic option. A transparent, thermoplastic gluewith an index of refraction of about 1.5 is desirable. It should bequite fluid at 180 degrees Fahrenheit (at least as mobile as honey atroom temperature). A material that has been discovered for this purposeis fructose. A particularly outstanding property of fructose is that itis water soluble and flammable solvents are not necessary to use inclean-up nor removal after the element has been exposed.

In preparing the fructose, the crystalline material is heated to about250 degrees F. and, with stirring, It soon becomes as liquid. It is thencooled to room temperature for future use. It remains clear, and quitehard.

The film, the retro-reflector, and the fructose is then placed in anoven set at 180 degrees F. The fluid fructose is placed between theretro-reflector and the emulsion side of the film. The layered assembly(film, glue, and retro-reflector) are placed between dark colored (asbrown) blotting paper sheets and the whole cranked slowly through aclothes washer wringer that is operated by hand (this allows slowmotion). This squeezes most of the excess glue from between the film andreflector.

(This same process can be used to make an improved Lippmann typephoto-sensitive element where a specular reflector is wanted, but thetoxicity and inconvenience of the liquid mercury is to be obviated. Thiscan be brought about by utilizing metallized mylar or by the specularside of common household aluminum foil. Additionally, this same processcan be utilized to make other non-Lippmann photo-sensitive elementswhere angular reflectors are used, as shown in U.S. Pat. No. 4,178,181,as described elsewhere in this disclosure, and as provided by thediffuse side of common household aluminum foil.)

The blotter adds some protection from light and at the same time absorbsthe glue that is squeezed from between the film and reflector. Thisassembly is put through the wringer several times so that the glue layeris very thin. Then it is cooled to room temperature, the blottersremoved, and the retro-reflecting photo-sensitive element (3-D film)cleaned up with a damp sponge. The 3-D film is ready for use. FIGS. 28and 31 can be referred to where the 3-D film is 3101, the 8E75 filmlayer is the photo-sensitive layer 3103 combined with thephoto-sensitive layer support 3104, the angular reflector is aretro-reflecting layer 2801 (and may include the protective paint 2807),and the glue layer is 3202. The preferred orientation of the 8E75 filmis as shown in FIG. 31; the emulsion layer side 3103 is closer to theangular reflecting layer 2801 than is the emulsion layer support side3104. The thickness of the 8E75 HD film (3103 plus 3104) was measured tobe 0.0071 inch. The thickness of the retro-reflecting layer 2801(including the protective paint layer 2807) was measured to be 0.0104inch. The total thickness of the 3-D film 3101 (with the glue layerincluded) is estimated at less than 0.020 inch. It is quite flexible.

After exposure, the retro-reflecting, photo-sensitive element 3101 (3-Dfilm) is again heated to 180 degrees, and the reflector peeled from thefilm. The film is cooled to room temperature. The film is then washed inroom temperature water until the water soluble glue (fructose) isdissolved. Processing by any of a variety of procedures then follows.

Camera for Taking 3-D Photographs with Retro-Reflecting, Photo-SensitiveElement

There is a difference In the technique and the camera that is used inordinary photography, that produces a 2-dimensional photograph, and thetechnique and camera that is used in producing 3-dimensional photographsas herein described.

Commonly, In ordinary photography, one wants great depth of field and inorder to obtain this desirable end, the effective lens diameter is madeas small as possible so that the scene viewed by different areas of thelens is the same.

In 3-dimensional photography, as described herein, one wants small depthof field and in order to obtain this desirable end, the effective lensdiameter is made as large as possible so that the scene viewed bydifferent areas of the lens is different and on purpose. It is best forthe F number to be 5 or less. In a digression, the size, weight, andcost of large lenses is a decided disadvantage. Fresnel lenses can beused to reduce weight and volume.

Human vision is such that subjects are seen 3-dimensionally in ahorizontal direction only (or along a line that passes through botheyes). If a 3-dimensional photographic system is to preserve thiscapability of horizontal 3-dimensionality, and be willing to sacrificethe capability of vertical 3-dimensionality (which is provided by around lens), the size and weight can be reduced substantially.Additionally, the inventor believes that by sacrificing vertical3-dimensionality the horizontal 3-dimensionality is improved. An axialview of a large lens is shown in FIG. 33 that would be suitable for usein a camera with a 4×5 inch film (or plate) format. The lens 3301 is 3inches in diameter and is capable of receiving more horizontal3-dimensional information than human eyes, which are separated by about21/2 inches. The center positions of the left eye 3302 and right eye3303 are shown.

In order to reduce the size and weight of the lens and to preserve thehorizontal 3-dimensional information gathering ability, the lens couldbe made elongate in a horizontal direction and reduced in a verticaldirection. To do this, the top 3304 and bottom 3305 of the lens isremoved. A weight and size efficient lens for a photographic system,that is to produce 3-dimensional photographs, is produced; the shape ishorizontally elongate. Thus, a camera design to facilitate the taking of3-dimensional photographs is accomplished by the use of a lens that ishorizontally elongate. Further weight and size reduction would beobtained by removing the center piece 3306. Prior art is stereoscopiccameras making stereoscopic paired photographs. The difference is thatthe 2 remaining lens pieces 3307 and 3308 have the same focal pointwhereas the 2 lenses of stereoscopic cameras have different focal pointsseparated by the lens spacing. The images from 3307 and 3308 are on topof each other whereas the images from the 2 lenses of a stereo cameraare separated by the lens separation The space 3306 could be used for abetween the lens finder, as is common to prior art stereo practice.

When the lens configuration used is horizontally elongated for thepurpose of weight and size efficiency, a second choice is available forthe configuration of the retro-reflecting layer. This is a groovedretro-reflector as shown in FIG. 32 and described in the specificationthat describes this figure. The system that results produces photographsthat are horizontally 3-dimensional and does so with a camera that isefficient in both size and weight.

Preferred Glue

In order to glue the layers together, in layered photo-sensitiveelements as shown in the disclosure, it was desired to obtain a gluewith the following requirements:

1. It should be transparent.

2. It should have an index of refraction close to 1.5.

3. It should be thermoplastic.

4. It should be quite hard at room temperature, but not brittle.

5. It should be quite fluid at 180 degrees F. (as viscous as thick honeyis at room temperature is adequate; even thinner is better).

6. It should be water soluble.

7. It should be non-toxic.

Substantial time was spent by the inventor in searching for materialsthat would meet the above specifications. No material was found.

Hence, an object of the invention is to find a material, meeting theabove requirements, that would be especially useful as a way oftemporarily glueing together the layers, in layered photo-sensitiveelements, and additionally one that would be useful as an index matchingmaterial for optical applications in general.

An application is to obtain a layered photo-sensitive element that isassembled by the manufacturer and that may be taken apart easily by theend user by the utilization of heat. Additionally, water clean-up ismost convenient, and it is desirable to have the residue easily removedby water rather than by solvents that are frequently flammable or toxicand water is usually available in photographic film processinglaboratories.

There are resinous materials that meet the above specifications, exceptfor the water solubility requirement.

The melting of dextrose and sucrose was tried. Sucrose was the worst asit was too viscous at 230 degrees F. and it turns brown. Dextrose wastoo viscous at 220 degrees The melting of fructose was tried. When thetemperature was raised to 250 degrees F. and stirred, it soon becameliquid. When cooled to 180 degrees, it met requirement number 5 (above).Fructose is by far the least viscous (thinnest) at 180 degrees F. Whencooled to room temperature, it met all the other requirements (above).At room temperature, the index of refraction was measured to be 1.523.Fructose can thus be used as a thermosetting optical cement. By addingsome water (less than 20%), the material can be made more fluid at roomtemperature and at 180 degrees F.; the mixture, or solution, is onecomprising fructose and water. It has been used successfully by theinventor in glueing together the layers of layered photo-sensitiveelements. After exposing the element to light, the reflecting layer waspeeled from the photo-sensitive layer after utilizing of heat.

Because the fructose glue is hygroscopic, photo-sensitive elements madewith the fructose glue should be stored in a dry environment to retardthe ingressing of moisture that can enter the glue layer around theedges. A small package of dessicant packed with the photo-sensitiveelements is beneficial.

Thus, a useful, non-obvious material was found that meets the above 7requirements for a material that is especially useful as a way oftemporarily glueing together the layers of layered photo-sensitiveelements. It is also useful as an index matching material for otheroptical applications.

The glue that results is stored at room temperature as a transparentsemi-solid mass. Being hygroscopic, it is kept in closed containers.

Preferred Illumination Sources for Subject

The preferred illuminating sources for subjects being photographed, asin this disclosure, is by one, or more, monochromatic source. Sourcesfor such light can be provided by lasers, gas discharge tubes, or whitelight sources (as from an incandescent source) filtered through narrowband filters.

The best mode is to use one or more monochromatic wavelengths asprovided by one or more lasers.

However, in attempting to use a laser to evenly illuminate a subject, acoarse speckle pattern resulted.

Background for the speckle pattern follows. If one desires to start witha white light source in the form of a beam, as provided by a flashlight,and to evenly illuminate a wide area, It is merely necessary to aim theflashlight beam at a diffuse surface, as the diffuse side of commonhousehold aluminum foil; the reflected light reflected from the foildoes provides even illumination over a wide area of the subject beingphotographed. The diffuse surface is a diffuser. If, however, onedesires to start with a monochromatic light source in the form of abeam, as provided by a laser, and to evenly illuminate a wide area, andone aims the laser beam at a diffuse surface, as the diffuse side ofcommon household aluminum foil, the reflected light from the diffuserdoes not provide even illumination over a wide area of the subject beingphotographed. Instead, a coarse speckle pattern results. When aphotograph of a subject so illuminated is made, the unwanted specklepattern shows up in the photograph. This is shown in FIG. 34 which showsthe laser 3401, laser beam 3402, point of impact 3403, diffuser 3404,diffused light 3405, and the subject being illuminated 3406.

No easy nor obvious way was known to the inventor of eliminating thespeckle pattern in a photograph that is produced by illuminating thesubject with a laser light source. Invention was needed.

Hence, an object of the invention is to find a way of eliminating thespeckle in a photograph that is produced by illuminating the subjectwith a laser light source.

It was discovered that by moving the diffuser during exposure (as with amotor) that the speckle pattern visually appeared to be of finer grainand that the pattern moved as the eye of the observer moved. Thephotograph that resulted (from using a laser with a moving diffuser)from the subject being illuminated this way showed no speckle pattern,even though it visually appeared that the subject was illuminated by afine speckle pattern. Hence, the object of the invention was fulfilled;a way was found of eliminating the speckle in a photograph that isproduced by illuminating the subject with a laser light source.

FIG. 35 shows the moving diffuser 3505, the laser 3501, laser beam 3502,point of impact 3503, moving diffuser motor drive 3504, diffused light3506, and subject being illuminated 3507. Additionally, a lense 3508 maybe placed in the laser beam 3502 to focus the laser beam to a point 3503(smaller than the width of the laser beam) at the point of impact, thusproviding a better point source of diffused monochromatic light thanwithout the lens. Also, a lens (not shown) may be placed between thesubject 3507 and diffuser 3505; when this is done, a convenient sourceof converging monochromatic light is available and may be focused to aremote point from which light diverges. This design is a reflectingdiffuser as provided by the diffuse side ocommon household aluminumfoil. It is attached to a flat disc that is mounted perpendicularly to arotating shaft. A rotational speed of the shaft of about 500 revolutionsper minute has been found satisfactory and the distance from the pointof impact to the axis of rotation is about 1 inch and the exposure timeis about 1 minute. Other means of providing motion to a similar diffuserwould be apparent to a person skilled in the art, as linear instead ofrotary motion. In the design shown in FIG. 35, the diffused light isprovided by way of reflection from a moving diffuser.

Diffused light may also be provided by transmission through a movingdiffuser; a laser beam can be aimed (or focused with a lens) to a pointon a ground glass surface and the diffused light that is transmittedthrough the ground glass is used to illuminate a subject beingphotographed. The ground glass is the moving diffuser. The ground glassmay be a disc and motion may be imparted to it by a motor. Other ways ofimparting motion to such a transparent diffuser would be apparent to aperson skilled in the art.

Photographic Systems that Utilize the Retro-Reflecting Photo-SensitiveElement

When a retro-reflecting photo-sensitive element is properly exposed tolight from a subject, processed, and illuminated, a 3-dimensional imageof the subject is formed. The photographic system may or may not employa focusing element.

A 3-dimensional photographic system that uses no lens or focusingelement is shown in FIG. 37 which shows the layered photo-sensitiveelement 3701 (which is a retro-reflecting photo-sensitive element),retro-reflecting layer 3702, photo-sensitive layer (emulsion layer)3703, emulsion layer support 3704, illumination source 3705 whichilluminates the subject 3706 with light 3707 that is reflected from thesubject 3706 along an incident light path 3708 to and through thephoto-sensitive layer 3703 to the retro-reflective layer 3702 whichreflects the incident light back along the incident light path 3708 as areflected ray so that the incident and reflected rays coincide buttravel in opposite directions. The incident and reflected rays interferewithin the light-sensitive layer 3703 and interference patterns of lightwaves result which are parallel planes separated by a distance equal to1/3rd of the wavelength (in air) of light present. The surface of theparallel planes is perpendicular to the incident and reflected lightrays. For this process to work, the interference of light waves isrequired. Higher resolution is required for recording the interferencepatterns of short wave light than of long wave light. Thephoto-sensitive layer must not only be able to but must actually recordthese patterns. When more than one wavelength of light is present and isto be recorded, the photo-sensitive layer must be capable of andactually record the interference patterns caused by all the lightpresent that one wants to record.

FIG. 37 shows a layered photo-sensitive element where one layer is aretro-reflecting layer and another layer is a photo-sensitive layer.FIG. 37 also shows the use of a retro-reflecting element as an essentialelement in a photographic system which produces a 3-dimensionalphotograph; here, the said retro-reflecting element is in the form of asheet. FIG. 37 shows a method for making a 3-dimensional photographwhere the subject is illuminated, and light from said subject exposes a"retro-reflecting photo-sensitive element."

After exposure and processing, the photograph, which is a product of alensless photographic system, is illuminated and the 3-dimensional imageviewed. The viewing of the 3-dimensional image requires the interferenceof light waves. Viewing the 3-dimensional image of the photograph isshown in FIG. 38 which shows the photograph 3801, the emulsion layer3802, the emulsion layer support 3803, the viewer 3804, the illuminationsource 3805 and black paint (the location of which is indicated by 3806but is not shown in the drawing) which may be applied to the photographon the side away from the viewer, here stated to be on the emulsionsupport layer 3803. The virtual image 3807 appears in 3 dimensions, asthough it were behind the photograph, as the correct, positive, ororthoscopic image. The photograph may also be viewed from the other sideas shown in FIG. 39 which shows the photograph 3801, the emulsion layer3802, the emulsion layer support 3803, the viewer 3901, the illuminationsource 3902 and black paint 3903, which is indicated but not shown,which may be applied to the photograph on the side away from the viewer,this time on the emulsion layer. A real image 3904 appears in 3dimensions, in front of the photograph, as the incorrect, reversed, orpseudoscopic image.

There are various ways that the photograph may be illuminated forviewing. The light may be diverging parallel, or converging. Thedirection from which the photograph may be illuminated is eitherperpendicular to the surface of the photograph or at an angle betweenzero and 90 degrees. The quality of the light may be white or irregularacross the spectrum. (The light of a gas discharge lamp, or light from alaser, are examples of an irregular sources.) The photograph may beviewed by any combination of the preceeding that would be apparent toone skilled in the art.

The preferred illumination condition is where a point source of whitelight is used and its position is close to the eye. (A "point source ofwhite light" is provided by an incandescent light bulb with a smallfilament and clear glass envelope, as a 12 volt stop light from anautomobile; this is in contrast to the white light provided by a frosted100 watt light bulb.) This is shown in FIG. 40 which is similar to FIG.38. FIG. 40 shows the photograph 3801, the viewing position 3804, andthe virtual image 3807. The point source of diverging light 4001 isshown close to the eye 3804 and a shield 4002 is shown to ensure thatonly light reflected light from the photograph reaches the eye 3804.

Another way of illuminating the photograph is from a point source oflight positioned optically at the eye. This is shown in FIG. 41 which issimilar to FIG. 38. FIG. 41 shows the photograph 3801, the viewingposition 3804, and the virtual image 3807. A point source of diverginglight 4101 is shown aimed at a beam splitter 4102 (which may be apellicle) where light is reflected onto the photograph. The photographis viewed through the beam splitter.

The methods of viewing the photograph (as above described) that resultfrom using no lens may also be used to view a photograph that resultsfrom using focusing elements (as refractive or a reflective element) andnext described.

A 3-dimensional photographic system that uses a lens as a focusingelement is shown in FIG. 42 which shows the subject 3706, light source3705, light 3707 traveling from the light source 3705 to illuminate thesubject 3706, light reflected 3708 from the subject 3706 to the lens4201 (refracting element), and the 3-dimensional image 4202 of thesubject 3706. The retro-reflecting photo-sensitive element 3701 of FIG.37 is placed at position 4203, 4204, or 4205 depending upon where theimage is to appear in the photograph, as behind, on, or in front of thephotograph. FIG. 42 shows, during exposure, a method for making a3-dimensional photograph where the subject is illuminated, and lightfrom said subject passes through at least one refractive element, andlight from said subject exposes a "retro-reflecting photo-sensitiveelement." This photographic system, that uses a refractive lens as afocusing element for making a 3-dimensional photograph, is the preferredand best mode of practicing the invention; it is shown in FIG. 42.

A 3-dimensional photographic system that uses a reflector as a focusingelement is shown in FIG. 43 which shows the subject 3706, light source3705, light 3707 traveling from the light source 3705 to illuminate thesubject 3706, light reflected 3708 from the subject 3706 to thereflector 4301 (reflecting element), and the 3-dimensional image 4302 ofthe subject 3706. The retro-reflective photo-sensitive element 3701 ofFIG. 37 is placed at position 4303, 4304, or 4305 depending upon wherethe image is to appear in the photograph, as behind, on, or in front ofthe photograph. FIG. 43 shows, during exposure, a method for making a3-dimensional photograph where the subject is illuminated, and lightfrom said subject is reflected by at least one reflective element, andlight from said subject exposes a "retro-reflecting photo-sensitiveelement."

These systems can be used to make a camera that takes colored3-dimensional photographs by making an enclosure that comprises the lensand the retro-reflective photo-sensitive element, and a means foradmitting light at will to make the exposure. This has beenaccomplished. It has been done by changing the nature of the reflectorused in the Lippmann process of color photography. It employs theinterference of light waves. During exposure, the distance between thecamera and the subject can move more than a wavelength of light.

A 3-dimensional photographic system that converts a series of2-dimensional cross sectional pictures of a 3-dimensional object into asingle 3-dimensional photograph is depicted in FIG. 44. The principal ofoperation is that the photographic system that comprises theretro-reflecting photo-sensitive element is used and a singleretro-reflecting photo-sensitive element is exposed by multipleexposures to the series of cross sectional pictures resulting in asingle photograph that contains all of the information of the 5 crosssections correctly displayed in space. It is a 3-dimensional montageinstead of the common 2-dimensional montage of artworks; each exposureis made with the image of each 2-dimensional cross section of the serieslocated at a different distance from the retro-reflectingphoto-sensitive element.

FIG. 44 shows the camera 4401, the retro-reflecting photo-sensitiveelement 4402, the lens 4403, and means 4404 for admitting light. Anillumination source is shown at 4405. A series of pictures, 5 in thisexample, are x-ray cross sections of a football, as a CAT Scan; Thex-rays are shown in plan view at 4416 through 4420. The outline of thefootball 4416 is added for visualization purposes; it is not actuallythere. There are different methods of positioning the images (4411-4415)of each of the cross sections (4416-4420) at different distances fromthe retro-reflecting photo-sensitive element 4402. One of the methodsfollows.

1. The first exposure is made with the first cross section 4416 locatedat the position indicated by 4406; the image to be recorded appears at4411. The cross section of the football is a ring and the intersectionof the ring with the plane of the paper is 2 dots as indicated by 4411.The 3-dimensional photograph, however, will show the entire ringpositioned appropriately in space.

2. The second exposure is made with the second cross section 4417located at the position indicated by 4407; the image to be recordedappears at 4412.

3. The third exposure is made with the third cross section 4418 locatedat the position indicated by 4408; the image to be recorded appears at4413.

4. The forth exposure is made with the forth cross section 4419 locatedat the position indicated by 4409; the image to be recorded appears at4414.

5. The fifth exposure is made with the fifth cross section 4420 locatedat the position indicated by 4410; the image to be recorded appears at4415

When the photo-sensitive element is processed and viewed, the footballwill appear as a series of rings suspended in space. The rings representthe intersection of the 5 cross sections through the surface of thefootball, and in this case x-ray pictures. A choice of 5 cross sectionsis illustrative only, more or less than 5 can be used.

FIG. 44 depicts a way that cross sectional pictures may be photographedwhere the pictures may be opaque and they are illuminated by reflectedlight from light source 4405. The light that reaches the film 4402 wasreflected from the pictures 4406-4410.

FIG. 44 depicts a 3-dimensional image that is about the same size as thecross-sectional pictures. The image may be made larger or smaller thanthe subject depending on the optics, relative positions of the crosssections, optical system, and retro-reflective photo-sensitive element.

Transparencies may be used instead of opaque pictures, so that lighttransmitted by the transparencies (the transparencies are back lighted)reaches the lens 4403 and the film 4402.

Instead of the cross sections 4406-4410 being pictures (which may bephotographs), A video display terminal may provide a sequence ofpictures that is photographed by the camera. One way of doing the is toposition the video display screen first at position 4406, and the firstexposure is made. Then the surface of the video display screen isrelocated to position 4407, and the second exposure is made. Thiscontinues until all cross sections have been photographed by the camera4401. The best mode of supplying light to the cross sections, whetherthe cross sections are pictures (opaque or transparent) or whether thecross sections are displayed on a video display terminal, is bymonochromatic light. The video display terminal should use internallythe trace a monochromatic light beam. One or more monochromatic lightsources may be used in each application.

FIG. 44 shows the sequence of pictures being taken where each of thesequence is positioned at a different distance from the camera lens4403. Another way that variable positioning of the cross sections may beaffected is by leaving the distance to the cross sections the same foreach picture but instead vary the conditions within the camera so thatthe image of each cross section falls at the desired distance (in frontof, on, or behind) from the film 4402. As an example of when videoinformation is being converted into a 3-dimensional image, it wouldprobably be most convenient for the distance from the camera 4401 to thevideo screen to remain constant and to vary the camera optics toposition each cross section (displayed on the video terminal) at thedesired position with respect to the film 4402. However, another way ofdoing it would be to leave the distance from the lens to the videoscreen constant and to vary the position of the film 4402 for eachexposure.

Another way of making a 3-dimensional image is to continually expose(leave the shutter 4404 open) as the subject moves in space (or as thevideo display terminal continually moves while the picture continuallychanges during the exposure). The 3-dimensional image in the photographthat results then displays a colored trail of the path of the lightemitting subject during exposure. This would be analagous to the case inordinary 2-dimensional photography when the lens is left open on a timeexposure and traffic lights on a distant roadway are recorded as whiteand red streaks that record the positions of headlights and tail lightsduring the exposure, except in this case, the streaks are seen in 3-D.

The use of this method of converting 2-dimensional cross section imagesof 3-dimensional objects to a single 3-dimensional photograph hasadvantages over other methods of doing so. One of the main areas ofapplication is to medical imaging.

The preferred embodiment is to use a photographic system that uses arefractive focusing element and a retro-reflective photo-sensitiveelement as the particular angular reflector, as shown in FIG. 42.

Some Details of the 3-Dimensional Process

The "retro-reflecting photo-sensitive" element:

1. The element is a layered assembly which includes (a) alight-sensitive (emulsion) layer, and (b) a parallel retro-reflectinglayer

2. The retro-reflecting layer is an "angular" reflector because it is areflecting sheet that reflects light at an angle to a specularlyreflected ray from the nominal surface. This is discussed elsewhere inthis specification; see FIG. 7.

3. The minimum thickness of the light-sensitive (emulsion) layer must beat least as thick as 2 planes (described elsewhere) for the process towork. The longer the wavelength, the farther apart the planes. Anotherway of saying the same thing is that the minimum thickness of thelight-sensitive (emulsion) layer must be at least equal to the longestwavelength of light (in air) to be recorded divided by 3. Therefore, ifwavelengths over the entire visible spectrum (400 to 700 nanometers) areto be recorded, the longest wavelength to be recorded is 700 nanometers,and the emulsion layer minimum thickness must be at least equal to 700divided by 3 equals 233 nanometers; it could be 600, but not 150nanometers thick.

The method of using the "retro-reflecting photo-sensitive" elementincludes the following essential steps during exposure:

4. The photo-sensitive element is exposed to light from only one side ofthe element. See FIG. 31.

5. The incident light and its reflection interfere, within thelight-sensitive (emulsion) layer, causing an interference pattern oflight waves to exist within the light-sensitive layer during exposure.

6. These patterns are a series of parallel planes of light (separated byplanes of darkness). The planes are not parallel to the reflectingsurface and assembly layers (except in the trivial case where anexposing ray is exactly perpendicular to the assembly layers) but areperpendicular to the exposing ray of incident light (within theemulsion); the distance apart is about 1/3rd of the wavelength (in air)of the light. The light-sensitive layer must be able to record theseplanes that are spaced as closely as 1/3rd of the shortest wavelength(in air) of the light to be recorded.

7. It is this angular orientation of the planes to the assembly layersthat makes a 3-dimensional image possible. It is because of thenon-angular orientation of the planes to the assembly layers in theLippmann process that makes a 3-dimensional image not possible. In theLippmann process, the planes are parallel to the assembly layers (theyare non-angular). In the process of the invention, which uses aretro-reflecting layer, the planes are not-parallel to the assemblylayers (they are angular).

8. During exposure, interference patterns (planes) produced by lightwaves are present within the light-sensitive layer. They are notparallel to the nominal surface of the reflector (except in the trivialcase where an exposing ray is exactly perpendicular to the assemblylayers). They are perpendicular to the exposing ray within the emulsion.

9. The light-sensitive layer is required to be able to record theseInterference patterns (planes).

10. The light-sensitive layer does record these interference patterns(planes). Or, the recording of the interference patterns of light waveswithin the light-sensitive layer takes place by exposing thelight-sensitive layer.

The method of using the "retro-reflecting photo-sensitive" elementincludes the following essential steps after exposure:

11. The retro-reflecting layer is removed.

12. Detecting the image (or viewing the photograph) requires theinterference of light waves.

13. Although surface relief may occur in the photograph, an element ofthe image is primarily manifested by reflection from partiallyreflecting, parallel planes within the emulsion layer of the photographrather than from surface relief.

The Pyrochrome Process

This information has been supplied by Dr. Tung H. Jeong, Professor ofPhysics, Lake Forest College, Lake Forest, Ill., 60045. This is aprocess for processing holograms. The inventor has found it useful forprocessing photographs exposed with angular reflectors. Dr. Jeong'ssheet is reproduced below.

Film and Plates for Making Holograms with HeNe Lasers

Holotest 8E75 HD film and plates can be used to make all types ofholograms, and the processing procedure is the same. Expose the emulsionwith approximately 200 ergs/cm². Experimentally, expose the hologram sothat within less than one minute of development the hologram turns darkbut not opaque (a density of 2.5 is best).

Processing Procedure: The "Pyrochrome" process.

1. Develop one minute in the prescription below:

Solution A: pyrogallol--10 gm/liter.

Solution B: sodium carbonate anhydrous--60 gm/l.

Mix equal parts of A and B just before use. It becomes bad after 10minutes, so use only enough for the hologram being developed anddispose. The above mixture yields a red image for reflection holograms.If a color shift is desired (toward orange, yellow, or green), add from0-25 gm/l of sodium sulfite to Solution A. (Pyrogallol is available atlarge chemical suppliers, like Fishers, American Scientific Products,Eastman Kodak, etc.)

2. Wash for 3 minutes.

3. Bleach until clear--15 seconds with maximum of 2 minutes.

Bleach solution: Potassium dichromate--4 gm/l and 4 ml/l of concentratedsulphuric acid.

4. Wash for 3 minutes.

5. Wash in Kodak Photo Flo solution for 2 minutes.

6. Hang up vertically to dry. For plates, rest hologram vertrically onpaper towels. Transmission holograms may be squeegeed.

Resolution Requirement of the Photo-Sensitive Layer Used with theRetro-Reflecting Layer

Resolution of the photo-sensitive layer must be at least equal to theshortest wavelength (in air) to be recorded divided by 3.

If the shortest wavelength to be recorded is 400 nanometers (deepviolet), the photo-sensitive layers must be able to resolve interferenceplanes that are separated by 400/3=133 nanometers; this is in adirection parallel to an incident exposing ray. The interference planesare perpendicular to the exposing ray. Within the photo-sensitive layer,the exposing ray can be up to about 42 degrees off the perpendicular tothe surface of the element when the index of refraction of thephoto-sensitive layer is 1.5. In the case where deep violet is to berecorded (400 nanometers), the resolution requirement is 7,500 planesper millimeter. Had the wavelength of interest been 700 nanometers, theresolution requirement would have been 4,290 planes per millimeter. Fromthese figures, it can be seen that the resolution requirement when aretro-reflecting layer is used (or for the Lippmann method of colorphotography) is much higher than for ordinary photography where aresolution of 200 lines per millimeter (in a direction parallel to thefilm surface) is considered high.

The photo-sensitive layer can be a silver halide emulsion layer. Whenthese grains are spherical, as is the Lippmann process, their averagediameter, is about 1/8th of the shortest wavelength of light to berecorded, or less, for adequate reproduction of color.

Although 8E75 HD film or plate (silver halide) has been stated inseveral places within this disclosure, a person skilled in the art wouldchoose many other types of photo-sensitive materials for thephoto-sensitive layer in a retro-reflecting photo-sensitive element forvarious applications and light sources. Among the other photo-sensitivematerials is dichromated gelatin. These and other photo-sensitivematerials suitable for various applications of the invention can befound in Collier, 1971; Wolf, 1983; Goodman, 1980; Smith, 1977; andJeong, 1982.

Best Mode

The best mode of making a retro-reflecting photo-sensitive element (3-DFilm) is shown in FIG. 31 where the retro-reflecting layer 2801,photo-sensitive layer (emulsion) 3103, photo-sensitive layer support3104 and the glue 3102 are shown. The retro-reflecting layer materialcan be obtained from Reflexlite Corp., 199 Whiting St., New Britain.Conn. 06050 and is designated as "A/C 1000, white, no adhesive." or "PC1000 with Tyvek backing, white." The former is preferred but the latteris more available. The photo-sensitive layer 3103 and its support 3104is Agfa-Gevaert 8E75HD film (or plate). The glue is fructose, made byheating granular fructose until it melts, and cooling to 180 degrees F.The 8E75HD and the retro-reflective layer are placed in an environmentof 180 degrees F. The film is placed flat, the fructose poured over it,and the reflector placed on top, with the reflecting surface toward theemulsion surface. All but a thin film of glue is removed by slowlyputting the assembly through rubber rollers (as hand operated clotheswashing wringer). The assembly is cooled to room temperature and a dampsponge can be used to clean up excess glue from the surfaces.

The best mode for utilizing the 3-D Film is described under the heading"Exemplary Method of Using the Invention."

Person Skilled in the Art

The specific industry or trade in which the practical manufacturingproblems are encountered and in which the invention is used is thephotographic film manufacturing industry. All of the above steps wouldbe best performed by a photographic film manufacturing company, asEastman Kodak Co., and sold to the public ready to use.

Different aspects of the invention involve distinct arts. The "personskilled in the art" is a team made up of experts skilled in the variousaspect of the invention. An example of such a team of experts is shownin Mees, 1961, page viii.

Brief Comparison. Photographs of the Invention and Prior Art.

There is a difference in the photographs resulting from the Lippmannprocess and the process of the invention. FIG. 46 depicts the Lippmannphotograph. FIG. 48 depicts the invention photograph.

The difference in the resulting photographs is depicted by the partiallyreflecting parallel planes of the figures. The image in both photographsis composed of these parallel planes. However, the planes of theinvention 4803 are at an angular relationship to the photograph'ssurface 4801, whereas the planes of the Lippmann process (prior art)4603 are at a non-angular relationship to the the photograph's surface4601 (as the planes are parallel to the photograph's surface). It isthis angular relationship of the planes 4803 that makes the3-dimensional imaging of the photo-sensitive element of the inventionpossible.

The invention's retro-reflecting photo-sensitive element 3101 of FIG. 31may be compared to the prior art Lippmann photo-sensitive element 101 OfFIG. 1.

Additionally, a comparison can be made by referring to FIGS. 45, 46, 47,& 48.

Essentials of the Lippmann photo-sensitive element are shown in FIG. 45;the photograph that results is shown in FIG. 46.

Essentials of the invention's retro-reflecting photo-sensitive elementare shown in FIG. 47; the photograph that results is shown in FIG. 48.

The Lippmann Photo-Sensitive Element.

When an exposing ray enters a Lippmann photo-sensitive element, it isreflected as shown in FIG. 45. FIG. 45 shows the Lippmannphoto-sensitive element 4501. The incident light ray 4502 passes throughthe photo-sensitive layer 4503, and is reflected by the surface 4504 ofthe ordinary (specular) reflector 4505 (of mercury) as the reflected ray4506.

An element of the image 4602, in the resulting photograph FIG. 46, isformed by partially reflecting planes 4603, within the emulsion layer4604, that are parallel to the surface of the photograph 4601 as shownin FIG. 46.

The Retro-Reflecting Photo-Sensitive Element.

When an exposing ray enters a retro-reflecting photo-sensitive element,it is reflected as shown in FIG. 47. FIG. 47 shows the retro-reflectingphoto-sensitive element 4701. The incident light ray 4702 passes throughthe photo-sensitive layer 4703 and is reflected by the retro-reflector4704 as the reflected ray 4705.

An element of the image 4802 in the resulting photograph FIG. 48 isformed by partially reflecting planes 4803, within the emulsion layer4804, that are at an angle to the surface of the photograph 4801 asshown in FIG. 48.

It is the ability (of the retro-reflecting photo-sensitive element ofthe invention) to form (in the completed photograph) partiallyreflecting layers that are at a particular angle to the surface of theresulting photograph that is responsible for the invention producing3-dimensional photographs.

Non-Angular and Angular Reflectors in Making 3-Dimensional Photographs

Inventor believes that angular reflecting surfaces within the emulsionlayer of the completed photograph are required in order to produce a3-dimensional image and that the use of an angular reflector duringexposure is required to produce said angular reflecting surfaces withinthe emulsion layer of the completed photograph.

FIG. 46 shows a completed photograph with non-angular reflectingsurfaces within the emulsion layer that result from using a non-angularreflector during exposure. They cannot produce a 3-dimensionalphotograph. A non-angular reflector was used by the prior art ofLippmann.

FIG. 48 shows a completed photograph with angular reflecting surfaceswithin the emulsion layer that result from using an angular reflectorduring exposure. They can produce a 3-dimensional photograph. An angularreflector was not used by the prior art of Lippmann. The first angularreflectors known to inventor are revealed in the application of 1966that resulted in U.S. Pat. No. 4,178,181.

Some angular reflectors used during exposure do not result in3-dimensional photographs.

Some angular reflectors used during exposure do result in 3-dimensionalphotographs. An example is a retro-reflector and inventor believes thatthere are other angular reflectors that also result in 3-dimensionalphotographs, although the retro-reflector (utilizing cube-corners formedby 3 intersecting surfaces) is the best mode for producing 3-dimensionalphotographs.

Exemplary Methods of Using the Invention

The preferred method for making a 3-dimensional photograph is with theuse of a lens, as shown in FIG. 42.

The focal length of the lens should be less than 5 times the lensdiameter (the f number is less than 5).

A suitable camera is obtained. Guidelines are provided in the part ofthis disclosure that is entitled "Camera for taking 3-D photographs. Onethat has proved to be useful is a Speed Graphic with a 4×5 inch format.A lens, that can be used to advantage, has a diameter of 2.63 inches andhas a focal length of about 3.25 inches. The distance of the lens 4201to the film 4204 is made equal to the distance of the lens 4201 to thesubject 3706 of FIG. 42.

A method for making a 3-dimensional photograph comprises a sequence ofthe following stems of:

1. providing film that is a layered photo-sensitive element wherein onelayer is a photo-sensitive layer and another layer is a retro-reflectinglayer. This film is shown in FIG. 31 wherein the layered photo-sensitiveelement is shown at 3101 and one layer that is a photo-sensitive layeris shown at 3103; another layer that is the retro-reflecting layer isshown at 2801. The retro-reflecting layer 2801 is glued to thephoto-sensitive layer 3103 by the glue shown at 3102. Thephoto-sensitive layer support is shown at 3104. The 8E75 film that isused is indicated by 3107. The thickness of the film indicated by 3101of FIG. 31 is about 0.020 inches and quite flexible.

The directions on how to make this retro-reflecting, photo-sensitiveelement are given in the portion of this disclosure that is entitled"How to Make a Retro-Reflecting, Photo-Sensitive Element." A film orglass plate holder is convenient. The film 3101 (retro-reflecting,photo-sensitive element) is placed in the film holder and placed in thecamera. A sheet that is less than 4×5 inches can be used and it can beheld in place by attaching it to the partition that divides the filmholder in two by the use of pressure sensitive tape.

2. illuminating the subject to be photographed. The set up is shown InFIG. 42 with the subject at 3706, the illumination source at 3705, thecamera lens at 4201, and the film (retro-reflecting photo-sensitiveelement) at 4204. The preferred illumination source 3705 is diffusedlight from a laser in order to provide a monochromatic light source (SeeFIG. 34.). If one monochromatic source is used, the photograph willappear in one color only. If more colors are desired in the photograph,the subject needs to be lighted by a plurality of monochromatic lightsources. As an example, a helium-neon laser can provide a redmonochromatic light source with a wavelength of 633 nanometers and aargon laser can provide a blue monochromatic light source with awavelength of 488 nanometers. Some lasers provide multiple monochromaticwavelengths and these can be selected for use at will. Gas dischargetubes (examples are mercury, sodium, or cadmium) also can provide one ormore monochromatic wavelengths. By suitable filtering of sources thatprovide multiple monochromatic wavelengths, the wavelengths of choicecan be obtained. Details of how diffused monochromatic light may be usedin illuminating the subject are shown in the part of this disclosurethat describes FIGS. 34 and 35. When the subject is illuminated withlight from a helium-neon laser as suggested, the energy density fallingon the subject can be made to equal about 3 micro-watts per squarecentimeter. If the subject is a polished coin, it can be oriented sothat one of the more or less flat sides of the coin reflects light intothe lens of the camera.

3. exposing the film (retro-reflecting, photo-sensitive element) withlight from the subject. The exposure can be about 45 seconds.

4. removing the reflecting layer from the photo-sensitive element. Thefilm (photo-sensitive element) is removed from the camera and heated inan oven to about 180 degrees F. The retro-reflecting layer is thenpeeled away from the photo-sensitive layer and the photo-sensitive layer(with support) cooled to room temperature (as 72 degrees). The glueresidue is removed by agitating the film in a container of running wateruntil the glue is dissolved-away. The glue feels slick, and its presencecan be felt by lightly rubbing the emulsion layer with a finger while itis being washed by water. Before processing, the image is invisible.

5. developing the photo-sensitive layer of the photo-sensitive elementto provide a 3-dimensional photograph. The best way known to inventorfor developing (or processing) is to use the "pyrochrome process."Processing makes the image visible. The details of this process aregiven under the heading, "The Pyrochrome Process". The inventor developsfor 1 minute, water washes for 3 minutes, bleaches for 1 minute, waterwashes for 3 minutes or more minutes. This step may be followed byplacing in Photo-flo solution for 1/2 minute. It is then dried. Theimage appears green (assuming that only one monochromatic light sourcewas used to expose the film and that was at 633 nanometers). The colorcan be corrected by immersing the photograph in a solution oftriethanolamine in water. This is discussed in Collier page 289. Anincandescent light source is commonly used for viewing the photograph.

6. painting the side of the photograph away from the observer. The sideof the photograph away from the observer is painted black. This isbecause the photograph is transparent where there was no light In thesubject. "No light" means blackness" and in order to make the photographappear black in areas where it is transparent, black paint is used. Theuse of almost any black paint helps. A particular one that has beenfound to be especially useful is Ultra Black #1602 Krylon, manufacturedby Borden, Inc., Columbus, Ohio 43215.

The film that was exposed in the camera forms the photograph and is apositive.

A method, for making a 3-dimensional photograph where the subject 3706is illuminated 3707 and light 3708 from the subject 3706 passes throughat least one refractive element 4201 and light 3708 from said subject3706 exposes a retro-reflecting photo-sensitive element at positions4203, 4204, or 4205, is shown in FIG. 42. (The retro-reflectingphoto-sensitive element 3101 of FIG. 31 is located at any one of thepositions indicated by 4203, 4204, or 4205 of FIG. 42.) Saidretro-reflecting photo-sensitive element 3101 comprises a layeredassembly that includes a photo-sensitive layer 3103 and aretro-reflecting layer 2801 in FIG. 31; it also comprises aphoto-sensitive layer support 3104.

A method, for making a 3-dimensional photograph where the subject 3706is illuminated 3707 and light 3708 from the subject 3706 is reflected byat least one reflective element 4301 and light 3708 from said subject3706 exposes a retro-reflecting photo-sensitive element at positions4303, 4304, or 4305, is shown in FIG. 43. (The retro-reflectingphoto-sensitive element 3101 of FIG. 31 is located at any one of thepositions indicated by 4303, 4304, or 4305 of FIG. 43.) Saidretro-reflecting photo-sensitive element 3101 comprises a layeredassembly that includes a photo-sensitive layer 3103 and aretro-reflecting layer 2802 in FIG. 31; it also comprises aphoto-sensitive layer support 3104.

A method for making a 3-dimensional photograph where the subject 3706 isilluminated 3707 and light 3708 from said subject 3706 exposes aretro-reflecting photo-sensitive element 3701 is shown in FIG. 37. Saidretro-reflecting, photo-sensitive element comprises a layered assembly3701 that includes a photo-sensitive layer 3703 and a retro-reflectinglayer 3702; it also comprises a photo-sensitive layer support 3704.

A photographic system for producing a 3-dimensional photographcomprising a retro-reflective photo-sensitive element is shown in FIG.37. The retro-reflecting photo-sensitive element 3701 comprises alayered assembly that includes a photo-sensitive layer 3703 and aretro-reflecting layer 3702; it also comprises a photo-sensitive layersupport 3704.

The use of a retro-reflective element 3702 as an essential element in aphotographic system that produces a 3-dimensional photograph is shown inFIG. 37. Said retro-reflective element 3702 is in the form of a sheet.(cl 20,21):

A layered photo-sensitive element 3701 wherein one layer is an angularreflecting layer 3702 and another layer is a photo-sensitive layer 3703is shown in FIG. 37. The preferred form of said angular reflecting layer3702 is a retro-reflecting layer.

A photographic system for producing a 3-dimensional photographcomprising a layered photo-sensitive element wherein at least one layeris a photo-sensitive layer and one layer is an angular reflector isshown in FIG. 37.

The layered photo-sensitive element 3701 is shown wherein at least onelayer is a photo-sensitive layer 3703 and one layer is an angularreflector 3702. Retro-reflecting layer 3702 is a particular kind ofangular reflector. Thus, 3702 is both an angular reflector and aretro-reflecting layer.

I claim the following:
 1. A layered photosensitive assembly comprising:aphotosensitive layer, and a reflecting layer, wherein during exposure,incident light passes through the photosensitive layer and is reflectedby the reflecting layer as reflected light, and the incident light andthe reflected light interfere with each other within the photo-sensitivelayer and form interference patterns of light waves which are recordedby the photo-sensitive layer, and a transparent layer between thereflecting layer and the photosensitive layer to facilitate theseparation of the reflecting layer from the photo-sensitive layer afterexposure.
 2. The invention of claim 1 wherein the reflecting layer isreflecting material.
 3. The invention of claim 1, said assemblycomprising2 separable units:the first unit comprising the photosensitivelayer, and the second unit comprising a reflecting layer.
 4. Theinvention of claim 3, wherein the 2 separable units are held fixed withrespect to each other during exposure by mechanical means.
 5. Theinvention of claim 3, wherein the 2 separable units are held fixed withrespect to each other during exposure by pneumatic means.
 6. Theinvention of claim 3, wherein the 2 separable units are held fixed withrespect to each other during exposure by hydraulic means.
 7. Theinvention of claim 1 wherein the transparent layer is characterized asbeing loosenable.
 8. The invention of claim 1 wherein the transparentlayer is characterized as being a glue.
 9. The invention of claim 1wherein the transparent layer is characterized as being an adhesivematerial.
 10. The invention of claim 1 wherein the transparent layer ischaracterized as being a pressure sensitive material.
 11. The inventionof claim 1 wherein the transparent layer is characterized as being aviscous fluid material.
 12. The invention of claim 1 wherein thetransparent layer is characterized as being a soluble material.
 13. Theinvention of claim 1 wherein the transparent layer is characterized asbeing a meltable material.
 14. The invention of claim 1 wherein thetransparent layer is characterized as being a thermoplastic material.15. The invention of claim 1 wherein the transparent layer material ischaracterized with an optical refractive index of about one and a half.16. The invention of claim 1 wherein the transparent layer comprisesfructose.
 17. The invention of claim 1 wherein the transparent layermaterial is characterized as being a solid.
 18. The invention of claim 1wherein the transparent layer material is characterized as being aliquid.
 19. The invention of claim 1 wherein the transparent layermaterial is characterized as comprising a wax.
 20. The invention ofclaim 1 wherein the transparent layer material is characterized ascomprising a resin.
 21. The invention of claim 1 wherein the transparentlayer material is characterized as comprising an oil.
 22. The inventionof claim 1 wherein the reflecting layer is characterized as being aspecular reflector, or a non-angular reflector.
 23. The invention ofclaim 1 wherein the reflecting layer is characterized as being anangular reflector.
 24. The invention of claim 1 wherein the reflectinglayer is characterized as being a diffraction grating.
 25. The inventionof claim 1 wherein the reflecting layer is characterized as beingreflective adhesive tape.